第26课 类的静态成员函数

#include <stdio.h>

class Test
{
private:
    int i;
    static int s_j;
public:

    int getI();
    static void StaticFunc(const char* s);
    static void StaticSetI(Test&d, int v);
    static int StaticGetJ();
};

int Test::getI()
{
    return i;
}

void Test::StaticFunc(const char* s)
{
    printf("StaticFunc: %s\n", s);
}

void Test::StaticSetI(Test&d, int v)
{
    d.i = v;
    //i = v;//静态成员函数不能访问非静态成员变量
    s_j = v;//合法，访问静态成员变量
}

int Test::StaticGetJ()
{
    return s_j;
}

int Test::s_j = 0;

int main()
{
    Test::StaticFunc("main Begin...");//通过类名调用静态成员函数

    Test t;

    Test::StaticSetI(t, 10); 

    printf("t.i = %d\n", t.getI());
    printf("s_j = %d\n", t.StaticGetJ());//通过对象名调用静态成员函数

    Test::StaticFunc("main End...");//通过类名调用静态成员函数    
    return 0;
}

#include <stdio.h>

class Test
{
private:
    static int cCount;
public:
    Test(){cCount++;}

    ~Test(){--cCount;}

     static int getCount(){return cCount;}
};

int Test::cCount = 0;


int main()
{
    printf("count = %d\n", Test::getCount());//0，通过类名调用函数

    Test t1;
    Test t2; 

    printf("count = %d\n", t1.getCount());//2， 通过对象名调用函数
    printf("count = %d\n", t2.getCount());//2， 通过对象名调用函数

    Test* pt = new Test();

    printf("count = %d\n", pt->getCount());//3

    delete pt;

    printf("count = %d\n", Test::getCount());//2，通过类名调用函数 
     
    return 0;
}