实例分析C++中重载、重写（覆盖）和隐藏的区别

标签：c++   多态   

函数重载:

在C++程序中，可以将语义、功能相似的几个函数用同一个名字表示，即函数重载。

重载从overload翻译过来，是指同一可访问区内被声明的几个具有不同参数列（参数的类型，个数，顺序不同）的同名函数，根据参数列表确定调用哪个函数，重载不关心函数返回类型。

class A{
public:
  void test(int i);
  void test(double i);
  void test(int i, double j);
  void test(double i, int j);
  int test(int i);         //错误，非重载
};

重载的实现:

几个同名的重载函数仍然是不同的函数，它们是如何区分的呢？我们自然想到函数接口的两个要素：参数与返回值。如果同名函数的参数不同（包括类型、顺序不同），那么容易区别出它们是不同的函数。

重载与覆盖成员函数被重载的特征：

（1）相同的范围（在同一个类中）；

（2）函数名字相同；

（3）参数不同；

（4）virtual 关键字可有可无。

覆盖是指派生类函数覆盖基类函数，特征是：

（1）不同的范围（分别位于派生类与基类）；

（2）函数名字相同；

（3）参数相同；

（4）基类函数必须有virtual 关键字。

翻译自override，也翻译成重写，是指派生类中存在重新定义的函数。其函数名，参数列表，返回值类型，所有都必须同基类中被重写的函数一致。只有函数体不同（花括号内），派生类调用时会调用派生类的重写函数，不会调用被重写函数。重写的基类中被重写的函数必须有virtual修饰。

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font-size: 1em !important; min-height: inherit !important; background: none !important;">A{</code></div><div class="line number4 index3 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; 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min-height: inherit !important; background: none !important;">  </code><code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">virtual</code> <code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">void</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; 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border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">B : </code><code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">public</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">A{</code></div><div class="line number11 index10 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">public</code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">:</code></div><div class="line number12 index11 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">    </code><code class="cpp comments" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 130, 0) !important; background: none !important;">//重写</code></div><div class="line number13 index12 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">virtual</code> <code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">void</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">fun3(</code><code class="cpp color1 bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: gray !important; background: none !important;">double</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">i){</code></div><div class="line number14 index13 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">    </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">cout << </code><code class="cpp string" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; color: blue !important; background: none !important;">"B::fun3() : "</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;"><< i << endl;</code></div><div class="line number15 index14 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">}</code></div><div class="line number16 index15 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">};</code></div><div class="line number17 index16 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp color1 bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: gray !important; background: none !important;">int</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">main(){</code></div><div class="line number18 index17 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">    </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">A a;</code></div><div class="line number19 index18 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">B b;</code></div><div class="line number20 index19 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">A * pa = &a;</code></div><div class="line number21 index20 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">pa->fun3(3);</code></div><div class="line number22 index21 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">pa = &b;</code></div><div class="line number23 index22 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">pa->fun3(5);</code></div><div class="line number24 index23 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp functions bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(255, 20, 147) !important; background: none !important;">system</code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">(</code><code class="cpp string" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; color: blue !important; background: none !important;">"pause"</code><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">);</code></div><div class="line number25 index24 alt2" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp spaces" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">  </code><code class="cpp keyword bold" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-weight: bold !important; font-size: 1em !important; min-height: inherit !important; color: rgb(0, 102, 153) !important; background: none !important;">return</code> <code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">0;</code></div><div class="line number26 index25 alt1" style="line-height: 15.3999996185303px; font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace; font-size: 14px; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px 1em !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; min-height: inherit !important; white-space: pre !important; background-image: none !important; background-attachment: initial !important; background-size: initial !important; background-origin: initial !important; background-clip: initial !important; background-position: initial !important; background-repeat: initial !important;"><code class="cpp plain" style="font-family: Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace !important; border-radius: 0px !important; border: 0px !important; bottom: auto !important; float: none !important; height: auto !important; left: auto !important; line-height: 1.1em !important; margin: 0px !important; outline: 0px !important; overflow: visible !important; padding: 0px !important; position: static !important; right: auto !important; top: auto !important; vertical-align: baseline !important; width: auto !important; box-sizing: content-box !important; font-size: 1em !important; min-height: inherit !important; background: none !important;">}</code></div>

重载和重写的区别：

（1）范围区别：重写和被重写的函数在不同的类中，重载和被重载的函数在同一类中。

（2）参数区别：重写与被重写的函数参数列表一定相同，重载和被重载的函数参数列表一定不同。

（3）virtual的区别：重写的基类必须要有virtual修饰，重载函数和被重载函数可以被virtual修饰，也可以没有。

隐藏规则:本来仅仅区别重载与覆盖并不算困难，但是C++的隐藏规则使问题复杂性增加了许多。这里“隐藏”是指派生类的函数屏蔽了与其同名的基类函数，规则如下：

（1）如果派生类的函数与基类的函数同名，但是参数不同。此时，不论有无virtual关键字，基类的函数将被隐藏（注意别与重载混淆）。

（2）如果派生类的函数与基类的函数同名，并且参数也相同，但是基类函数没有virtual关键字。此时，基类的函数被隐藏（注意别与覆盖混淆）。

隐藏和重写，重载的区别：

（1）与重载范围不同：隐藏函数和被隐藏函数在不同类中。

（2）参数的区别：隐藏函数和被隐藏函数参数列表可以相同，也可以不同，但函数名一定同；当参数不同时，无论基类中的函数是否被virtual修饰，基类函数都是被隐藏，而不是被重写。

#include<iostream>
using namespace std;
class A{
public:
  void fun1(int i, int j){
    cout << "A::fun1() : " << i << " " << j << endl;
  }
  void fun2(int i){
    cout << "A::fun2() : " << i << endl;
  }
  virtual void fun3(int i){
    cout << "A::fun3(int) : " << i << endl;
  }
};
class B : public A{
public:
    //隐藏
  void fun1(double i){
    cout << "B::fun1() : " << i << endl;
  }
    //重写
  void fun3(int i){
    cout << "B::fun3(int) : " << i << endl;
  }
    //隐藏
  void fun3(double i){
    cout << "B::fun3(double) : " << i << endl;
  }
};
int main(){
  B b;
  A * pa = &b;
  B * pb = &b;
  pa->fun3(3);        //重写，多态性，调用B的函数
  b.fun3(10);         //隐藏，调用B的函数
  pb->fun3(20);       //隐藏，调用B的函数
  system("pause");
  return 0;
}

很多C++程序员没有意识到有“隐藏”这回事。由于认识不够深刻，“隐藏”的发生可谓神出鬼没，常常产生令人迷惑的结果。
下面pb 和pd 指向同一地址，按理说运行结果应该是相同的，可事实并非这样。

#include <iostream>
using namespace std;
class Base
{
public:
	virtual void f(float x){ cout << "Base::f(float) " << x << endl; }
	void g(float x){ cout << "Base::g(float) " << x << endl; }
	void h(float x){ cout << "Base::h(float) " << x << endl; }
};
class Derived : public Base
{
public:
	virtual void f(float x){ cout << "Derived::f(float) " << x << endl; }
	void g(int x){ cout << "Derived::g(int) " << x << endl; }
	void h(float x){ cout << "Derived::h(float) " << x << endl; }
};
void main(void)
{
	Derived d;
	Base *pb = &d;
	Derived *pd = &d;
	// Good : behavior depends solely on type of the object
	pb->f(3.14f); // Derived::f(float) 3.14
	pd->f(3.14f); // Derived::f(float) 3.14
	// Bad : behavior depends on type of the pointer
	pb->g(3.14f); // Base::g(float) 3.14
	pd->g(3.14f); // Derived::g(int) 3 (surprise!)
	// Bad : behavior depends on type of the pointer
	pb->h(3.14f); // Base::h(float) 3.14 (surprise!)
	pd->h(3.14f); // Derived::h(float) 3.14
}

个人觉得：

pd->g(3.14f); // Derived::g(int) 3 (surprise!)

而

	pb->g(3.14f); // Base::g(float) 3.14

而调用h函数过程中，由于基类Base中没有加virtual关键字，所以不是覆盖，另外由于基类、派生类中的函数名、参数完全一样，所以不是重载，只能是正常的调用了。应该可以作“隐藏”理解，但是为什么pb的是调用基类的，pd的调用派生类的，还不是很理解，有大神理解的请指点下，谢谢！

	// Bad : behavior depends on type of the pointer
	pb->h(3.14f); // Base::h(float) 3.14 (surprise!)
	pd->h(3.14f); // Derived::h(float) 3.14

实例分析C++中重载、重写（覆盖）和隐藏的区别

标签：c++   多态   

原文地址：http://blog.csdn.net/xueruifan/article/details/46573825