C++:this指针

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this指针

在类的成员函数（不包括静态成员函数）中，存在一个名为this的指针，该指针指向成员函数被调用时的对象。

class clock {
    int second, minute, hour;
public:
    clock(int h, int m, int s)
       : hour(h), minute(m), second(s)
    {
    }
    void show_time() {
        cout <<  second << minute << hour;
        //等价于 cout << this->second << this->minute << this->hour;
    }
};
int main() {
    clock  t1(10, 20, 30), t2(20, 30, 10);
    t1.show_time();
    t2.show_time();
}

class clock {
public:
    clock &set_second(int n);
    clock &set_minute(int n);
    clock &set_hour(int n);
};
clock &clock::set_second(int n) {
    second = n;
    return *this;
}
int main() {
    clock time(1999, 9, 9);
    time.set_second(20);
    time.set_minute(30)
    time.set_hour(10);
    time.set_second(20).set_minute(30).set_hour(10);
}

this有两种类型：以clock类为例，clock* const和const clock* const

class clock {
public:
    void show_time() const {
        cout <<  second << minute << hour;
        second++;                  //error this类型为const Date *this

        clock *p = (clock*)(this); // 或者clock *p = const_cast<clock*>(this);
        p->second++; //ok
    }
};

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