C++之重写运算符练习

 1 #include<iostream>
 2 #include<string>
 3 using namespace std;
 4 
 5 class MyString{
 6 private:
 7     char* cp;
 8 public:
 9     MyString(char*);
10     ~MyString();
11     MyString(MyString&ms);
12     MyString& operator +(MyString&);
13     MyString&operator=(MyString&);
14     MyString&operator+=(MyString&);
15     char operator[](int i);
16     char* getP();
17 
18 };
19 MyString::MyString(char*cp=NULL):cp(cp){
20 }
21 MyString::~MyString(){}
22 MyString::MyString(MyString&ms){//深复制
23     int len = strlen(ms.cp);//先确定原来字符串长度
24     char*tempcp = new char[len+1];//开辟足够的空间
25     strcpy(tempcp,ms.cp);//复制相同的内容
26     cp = tempcp;//初始化对象的指针
27 }
28 
29 MyString& MyString:: operator +(MyString&ms){
30     int len = strlen(cp) + strlen(ms.cp);
31     char *tempcp = new char[len+1];
32     strcpy(tempcp,cp);
33     strcat(tempcp,ms.cp);
34     
35     return *(new MyString(tempcp));//不改变两边对象的内容，返回一个新的对象
36 }
37 MyString&MyString::operator=(MyString&ms){
38     if (cp == NULL || strlen(cp) < strlen(ms.cp)){
39         if (cp){
40             delete[] cp;//释放原来的小空间
41         }
42         cp = new char[(strlen(ms.cp) + 1)];//开辟足够的空间
43     }
44     cp=strcpy(cp, ms.cp);//复制内容
45     return *this;
46 }
47 MyString& MyString::operator+=(MyString&ms){
48 
49     char*tempcp = cp;//暂存cp,因为要重新开辟空间//如果直接使strcat空间不够会出错
50     cp = new char[strlen(cp)+strlen(ms.cp)+1];
51     strcpy(cp,tempcp);
52     strcat(cp,ms.cp);
53     
54     return *this;
55 }
56 char MyString::operator[](int i){
57     return cp[i];
58 }
59 char*MyString::getP(){//用于主函数中查看对象内容
60     return cp;
61 }
62 int main(){
63     MyString ms1("hello"),ms2("world");
64     cout << "+result:" << (ms1 + ms2).getP() << endl;
65     ms1 += ms2;
66     cout << "+=result:" << ms1.getP() << endl;
67     ms1 = ms2;
68     cout << "=result:" << ms1.getP() << endl;
69     cout << "[]result:" << ms1[0] << endl;
70 
71 }