一些构造函数代码之间的 C++ 区别

Question

代码是什么:

class Time {
    private:
        int hours;
        int minutes;
        int seconds;
    public:
        Time() { hours = 0; minutes = 0; seconds = 0; }
};

不同于:

class Time {
    public:
        Time();

    private:
        int hours;
        int minutes;
        int seconds;
};

Time::Time() {
    hours = 0;
    minutes = 0;
    seconds = 0;            
}

抱歉，如果问题过于简单，但我是 C++ 的新手。我运行了这两个代码，但没有发现任何区别...

Answer 1

class Time {
    private:
        int hours;
        int minutes;
        int seconds;
    public:
        Time() { hours = 0; minutes = 0; seconds = 0; }
};

此代码声明并定义了 Time 类的默认构造函数。

class Time {
    public:
        Time();

    private:
        int hours;
        int minutes;
        int seconds;
};

Time::Time() {
    hours = 0;
    minutes = 0;
    seconds = 0;            
}

此代码在类定义中声明了 Time 类的默认构造函数，然后在类定义之外对其进行了定义。通常两者会被分成Time.h 和Time.cpp，如下所示:

Time.h

class Time {
    public:
        Time();

    private:
        int hours;
        int minutes;
        int seconds;
};

时间.cpp

#include "Time.h";

Time::Time() {
    hours = 0;
    minutes = 0;
    seconds = 0;            
}