状态模式

【1】什么是状态模式？

不同的状态，不同的行为。或者说，每个状态有着相应的行为。

【2】状态模式的代码示例：

代码示例：

#include <iostream>
#include <string>
using namespace std;

class Work;
class State;
class ForenonnState;


class State
{
public:
    virtual void writeProgram(Work*) = 0;
};

class Work
{
public:
    int hour;
    State *current;
    Work();
    void writeProgram()
    {
        current->writeProgram(this);
    }
};

class EveningState : public State
{
public:
    void writeProgram(Work *w)
    {
        cout << "当前时间: " << w->hour << "心情很好，在看《明朝那些事儿》，收获很大！" << endl;
    }
};

class AfternoonState : public State
{
public:
    void writeProgram(Work *w)
    {
        if (w->hour < 19)
        {
            cout << "当前时间: " << w->hour << "下午午睡后，工作还是精神百倍!" << endl;
        }
        else
        {
            w->current = new EveningState();
            w->writeProgram();
        }
    }
};

class ForenonnState : public State
{
public:
    void writeProgram(Work *w)
    {
        if (w->hour < 12)
        {
            cout << "当前时间: " << w->hour << "上午工作精神百倍!" << endl;
        }
        else
        {
            w->current = new AfternoonState();
            w->writeProgram();
        }
    }
};

Work::Work()
{
    current = new ForenonnState();
}

int main()
{
    Work *w = new Work();
    w->hour = 21;
    w->writeProgram();
    return 0;
}
//Reuslt:
//当前时间: 21心情很好，在看《明朝那些事儿》，收获很大！