一.类对象作为类成员

代码： 

#include <iostream>
using namespace std;
class phone {
public:
	string shouji;
	phone(string shouji1) :shouji(shouji1) {
		cout << "phone的构造函数调用" << endl;
	}
	~phone() {
		cout << "phone的析构函数调用" << endl;
	}
};
class person {
public:
	int age;
	string name;
	phone shouji;
	//隐式转换相当于shouji=phone(shouji1)
	person(int a, string name1, string shouji1) :age(a), name(name1), shouji(shouji1) {
		cout << "person的构造函数调用" << endl;
	}
	~person() {
		cout << "person的析构函数调用" << endl;
	}
};
void fun() {
	person p(23, "小明", "苹果");
}
int main() {
	fun();
	return 0;
}

 注意：

二.静态成员 

2.1静态成员变量

代码： 

#include <iostream>
using namespace std;
class person {
public:
	static int age;
};
int person::age = 10;
void fun() {
	person p;
	p.age = 90;
	person p1;
	cout << p1.age << endl;
}
int main() {
	fun();
	return 0;
}

代码： 

#include <iostream>
using namespace std;
class person {
public:
	static int age;
};
int person::age = 10;
void fun() {
	person p;
	p.age = 90;
	cout << person::age << endl;
}
int main() {
	fun();
	return 0;
}

2.2静态成员函数

代码： 

#include <iostream>
using namespace std;
class person {
public:
	static int age;
	static void fun(int a) {
		age = a;          //只能调用静态成员变量
		cout << "静态函数fun调用" << endl;
	}
};
int person::age = 100;
void dioayong() {
	person p;
	p.fun(99);          //对象调用
	person::fun(66);   //类名调用
	cout << p.age << endl;
}
int main() {
	dioayong();
	return 0;
}

 三.this指针

3.1成员变量和函数的存储

代码： 

#include <iostream>
using namespace std;
class person {

};
void fun() {
	person p;
	cout<<sizeof(p);
}
int main() {
	fun();
	return 0;
}

代码： 

#include <iostream>
using namespace std;
class person {
public:
	int a;
	char b;
};
void fun() {
	person p;
	cout<<sizeof(p);
}
int main() {
	fun();
	return 0;
}

代码： 

#include <iostream>
using namespace std;
class person {
public:
	int a;
	static int b;
	void fun() {
		cout << "fun函数调用" << endl;
	}
	static void fun1() {
		cout << "fun1函数调用" << endl;
	}
};
int person::b = 10;
void fun() {
	person p;
	cout<<sizeof(p);
}
int main() {
	fun();
	return 0;
}

 3.2this指针使用

 代码：

#include <iostream>
using namespace std;
class people {
public:
	int age;
	people(int age) {
		this->age = age;
	}
};
void zhixing() {
	people p(10);
	cout << p.age << endl;
}
int main() {
	zhixing();
	return 0;
}

#include <iostream>
using namespace std;
class people {
public:
	int age;
	people(int age) {
		this->age = age;
	}
	 people& add(const people& p) {
		this->age += p.age;
		return *this;
	}
};
void zhixing() {
	people p1(10);
	people p2(20);
	p2.add(p1).add(p1).add(p1).add(p1);
	cout << p2.age << endl;
}
int main() {
	zhixing();
	return 0;
}

四.空指针访问成员函数

代码: 

#include <iostream>
using namespace std;
class person {
public:
	int age;
	void fun1() {
		cout << "fun1调用" << endl;
	}
	void fun2() {
		cout << "fun2调用" << age << endl;
	}

};
void diaoyong() {
	person* p = NULL;
	p->fun1();
	p->age = 10;
	p->fun2();
}
int main() {
	diaoyong();
	return 0;
}

 代码：

#include <iostream>
using namespace std;
class person {
public:
	int age;
	void fun1() {
		cout << "fun1调用" << endl;
	}
	void fun2() {
		if (this == NULL) {
			return;
		}
		cout << "fun2调用" << age << endl;
	}

};
void diaoyong() {
	person* p = NULL;
	p->fun1();
	p->fun2();
}
int main() {
	diaoyong();
	return 0;
}

 五.const修饰成员函数

 5.1常函数

代码： 

#include <iostream>
using namespace std;
class person {
public:
	int age;
	void showage(int m) const{
	//	age = 89; //报错
		m = 100;
		cout << "age=" << age <<" m=" << m << endl;
	}
};
void fun() {
	person p;
	p.age = 10;
	p.showage(7);
}
int main() {
	fun();
	return 0;
}

#include <iostream>
using namespace std;
class person {
public:
	mutable int age;
	void showage(int m) const{   //常函数
		age = 89; //报错
		m = 100;
		cout << "age=" << age <<" m=" << m << endl;
	}
};
void fun() {
	person p;
	p.age = 10;
	p.showage(7);
}
int main() {
	fun();
	return 0;
}

5.2 常对象

 代码：

#include <iostream>
using namespace std;
class person {
public:
	mutable int age;
	void showage1(int m) const{
		//age = 89; //报错
		m = 100;
		cout << "age=" << age <<" m=" << m << endl;
	}
	void showage2(int m)  {
		age = 89;
		m = 100;
		cout << "age=" << age << " m=" << m << endl;
	}
};
void fun() {
	const person p;
	p.age = 10;      
	p.showage1(7);
	//p.showage2(7);  报错  
}
int main() {
	fun();
	return 0;
}

 六.友元

友元关键字：friend

6.1全局函数做友元 

 代码：

#include <iostream>
using namespace std;

class home {
friend void func(home& p);
public:
	home(string keting, string woshi, string cuosuo):keting(keting),woshi(woshi),cuosuo(cuosuo) {

	}
	string keting;
private:
	string woshi;
protected:
	string cuosuo;
};

void func(home &p) {
	
	cout << p.keting << ' ' << p.woshi << ' ' << p.cuosuo << endl;
}
void fun() {
	home p("客厅", "卧室", "厕所");
	func(p);
}
int main() {
	fun();
	//cout << p.keting << ' ' << p.woshi << ' ' << p.cuosuo << endl;
	//保护和私有属性的不能访问
	return 0;
}

6.2类做友元 

​​#include <iostream>
using namespace std;

class building {
friend class goodgay;   //声明友元类
public:
	building();
	string keting;
private:
	string cesuo;
protected:
	string woshi;
};
building::building() {
	keting = "客厅";
	cesuo = "厕所";
	woshi = "卧室";
}

class goodgay {
public:
	goodgay();
	void show();
private:
	building* p;
};
void goodgay::show() {
	cout << this->p->keting << ' ' << this->p->cesuo << ' ' << this->p->woshi << endl;
}
goodgay::goodgay() {
	p = new building;
}
void f() {
	goodgay a;
	a.show();
}
int main() {
	f();
	return 0;
}

 6.3成员函数做友元

 代码：

#include <iostream>
using namespace std;
class building;
class goodgay {
public:
	goodgay();
	void show1(building& p);
private:
	building* p;
};

class building {
friend void goodgay::show1(building& p);   //声明友元类
public:
	building();
	string keting;
private:
	string cesuo;
protected:
	string woshi;
};
building::building() {
	keting = "客厅";
	cesuo = "厕所";
	woshi = "卧室";
}


void goodgay::show1(building& p1) {
	cout <<p1.keting << ' ' << p1.cesuo << ' ' << p1.woshi << endl;
}
//void goodgay::show2() {
//	cout << this->p->ketipng << ' ' << this->p->cesuo << ' ' << this->p->woshi << endl;
//}
//无权限
goodgay::goodgay() {
	p = new building;
}
void f() {
	goodgay a;
	building b;
	a.show1(b);
}
int main() {
	f();
	return 0;
}