类名 (const 类名 &) ；

class A
{private:int a;int b;public:A(int x,int y):a(x),b(y){} //构造函数初始化列表A(const A &obj) //拷贝构造函数{// 构造函数的主体}
};

int main(int argc, char const *argv[])
{A i(1,2);A j = i; //调用了拷贝构造A k(i); //调用了拷贝构造return 0;
}

省略复制

#include <iostream>
#include<string.h>
using namespace std;
class A
{private:char buf[16];public:A(const char *str){strcpy(buf,str);cout << "构造函数" << endl;}A(const A& a){strcpy(this->buf,a.buf);cout << "拷贝构造" << endl;}
};
int main()
{A ob = "nihao";return 0;
}

#include <iostream>
#include<string.h>
using namespace std;
class A
{private:char buf[16];public:A(const char *str){strcpy(buf,str);cout << "构造函数" << endl;}A(const A& a){strcpy(this->buf,a.buf);cout << "拷贝构造" << endl;}
};
A fnn()
{return A("nihao");
}
//或
A fuu()
{A a("nihao");return a;
}
int main()
{A ob = fuu();return 0;
}

this 指针

class A
{private:int a;int b;public:A(int x,int y):a(x),b(y){} //构造函数初始化列表void fun(){this->a = 4; //this 就是该对象的地址(*this).b = 5; //*this 就相当于对象本身}
};

class A
{private:int a;int b;public:A(int x,int y):a(x),b(y){} //构造函数初始化列表void fun(int a,int b){//a = a; //erreor ,系统会以为是形参 a 赋值给形参 a，并不会改变成员变量的值//b = b; //同上理this->a = a;this->b = b;}
};

void sun ( A * this );

void fun ( int a , int b , A * this );

A a ( 1 , 2 );

a . sun (& a );

a . fun ( 1 , 2 ,& a );

类的静态成员函数

class person
{
public:static void func(); //只需要在类内进行声明
};

int main(int argc, char const *argv[])
{A::fun();return 0;
}

class A
{private:int a;int b;static int c;public:static void fun();
};
int A::c = 0; //静态成员变量初始化

#include <iostream>
#include<string.h>
using namespace std;
class A
{private:int a;int b;public:static int c;static void fun(){cout << c << endl;}
};
int A::c = 0;
int main(int argc, char const *argv[])
{A a;a.c = 0;A::c = 5;a.fun();return 0;
}

友元函数和友元类(friend)

友元函数

#include <iostream>
#include<string.h>
using namespace std;
class A; //对 A 进行超前声明，不然 sun 参数找不到
int sun(int a,int b,A& c);
class A
{private:int x;int y;public:A(int a,int b):x(a),y(b){}~A(){}friend int sun(int a,int b,A& c);
};
int sun(int a,int b, A& c)
{c.x = a;c.y = b;return c.x+c.y;
}
int main(int argc, char const *argv[])
{A a(2,4);sun(1,2,a);return 0;
}

#include <iostream>
#include<string.h>
using namespace std;
class A; //对 A 进行超前声明，不然 sun 参数找不到
class B
{private:int i; char j;public:B(int a,char c){i = a;j = c;}~B(){}int fun(A *rm);
};
class A
{private:int x;int y;public:A(int a,int b):x(a),y(b){}~A(){}friend int B::fun(A* rm); //友元
};
int B::fun(A *rm)
{i = rm->x + rm->y;j = 'a';return i;
}
int main(int argc, char const *argv[])
{A a(2,4);B b(2,'A');b.fun(&a);return 0;
}

#include <iostream>
#include<string.h>
using namespace std;
class A; //对 A 进行超前声明，不然 sun 参数找不到
class B
{private:int i; char j;public:B(int a,char c){i = a;j = c;}~B(){}int fun(A &a);
};
class A
{private:int x;int y;friend B;public:A(int a,int b):x(a),y(b){}~A(){}
};
int B::fun(A &a)
{i = a.x + a.y;return i;
}
int main(int argc, char const *argv[])
{A a(2,4);B b(2,'A');b.fun(a);return 0;
}