C++：类的封装

●参数初始化列表

1、带参构造

类名(int参数1，int参数2....)

{

属性1 =参数1;

属性2 =参数2;

}

2、初始化列表

类名(<类型1>参数1， < 类型2>参数2...): 属性1(参数1)，属性2(参数2)

{

代码：

#include 
using namespace std;
class Car
{
public:
#if 1
    Car()
    {
        cout << "Car构造函数" << endl;
    }
#endif
    Car(string brand, string color):c_brand(brand),c_color(color)
    {
        cout << "have arg construct" << endl;
        //c_brand = brand;
        //c_color = color;
    }
    Car(int num):c_num(num)
    {
    }
    ~Car()
    {
        cout << "Car析构函数" << endl;
    }
    string c_brand;
    string c_color;
    int c_num;
};
 
class Person
{
public:
    Person()
    {
        m_name = "zs";
        m_age = 23;
        cout << "Person构造函数" << endl;
    }
 
    Person(Car c1)
    {
        m_car = c1;
        cout << "Person构造函数" << endl;
    }
 
    ~Person()
    {
        cout << "Person析构" << endl;
    }
    void PersonInfo()
    {
        cout << "name:" << m_name << endl;
        cout << "age:" << m_age << endl;
        cout << "car:" << m_car.c_brand << " #color:" << m_car.c_color << endl;
    }
 
    string m_name;
    int m_age;
    Car m_car;
};
class Dog
{
public:
    ~Dog()
    {
        cout << "dog析构" << endl;
    }
};
 
#if 0
void test01()
{
    Dog d1;
    Person p1;
    p1.m_car.c_brand = "bmw";
    p1.m_car.c_color = "black";
    p1.PersonInfo();
}
#endif
 
void test02()
{
    Car c1("bmw", "pink");
    Person p1(c1);
    p1.PersonInfo();
}
void test03()
{
    Person p2;
    p2.PersonInfo();
}
 
int main()
{
    test03();
    return 0;
}

 

●组合思想

- ==一个类包含一个或多个其他类的对象.==

构造与析构顺序:先构造类中的对象,再构造自身，析构顺序与构造相反.

#include 
using namespace std;
 
 
class Car
{
	public:
		Car()   //必须有无参数
		{
			cout<<"no agr construct"<
		}
		Car(string brand,string color):c_brand(brand),c_color(color)
		{
	
			cout<<"have agr construct"<
		}
		string c_brand;
		string c_color;
};
class Person
{
	public:
		void PersonInfo()
		{
			cout<<"name:"<
			cout<<"age:"<
			cout<<"car:"<"#color:"<
		}
		string m_name;
		int m_age;
		Car m_car;
 
};
 
 
void test01()
{
	Person p1;
	p1.m_car.c_brand="bmw";
	p1.m_car.c_color="black";
	p1.PersonInfo();
}
 
 
int main(int argc, char *argv[])
{
 
	test01();
	return 0;
}

●对象模型与this指针

（1）对象的成员属性与成员方法其实是分开存储的，类中的所有成员方法都只有一份实例

（2）只有非静态成员属性才会占用对象空间，使用sizeof运算符来验证

*对象模型

#include 
using namespace std;
 
class Animal
{
	public:
		int a_age;
		int a_num;
		void AnimalInfo()
		{
			cout<<"age:"<"num:"<
		}
};
 
void test01()
{
	Animal a1;
	cout<<sizeof(a1)<
}
 
int main(int argc, char *argv[])
{
	test01();
	return 0;
}

（3）this指针是每一个非静态成员函数都拥有的参数,只是该参数被编译器隐藏，但是可以在函数内使用

*对象模型与this指针

#include 
using namespace std;
 
class Animal
{
public:
    Animal(){}
    Animal(string a_name)
    {
        this->a_name = a_name;
    }
    int a_age;
    int a_num;
    string a_name;
 
    void AnimalInfo()
    {
        cout << "name:" << this->a_name << " num:" << this->a_num << endl;
    }
 
    Animal AgeAdd()
    {
        this->a_age += 1;
        return *this;    //a2.AgeAdd().AgeAdd().AgeAdd()
    }
};
 
void test01()
{
    Animal a1;
    //cout << sizeof(a1) << endl;
    a1.a_num = 34;
    a1.a_name = "yangtuo";
    a1.a_age = 5;
    a1.AnimalInfo();  //this ---> a1
 
    Animal a2("sheep");  
    a2.AnimalInfo();  //this ---> a2
}
 
int main()
{
    test01();
    return 0;
}
 

（4）this指针: == 指向当前调用成员函数的对象.

class Person

{

int PersonFun(int n)

{

this->num = n;

}

int num;

}

*this指针

#include 
using namespace std;
class Animal
{
	public:
		Animal()
		{
			a_age=0;
		}
 
		Animal(string a_name)
		{
			this->a_name=a_name;
		}
		~Animal()
		{
			cout<<"析构函数"<
		}
		int a_age;
		int a_num;
		string a_name;
	
	void Animallnfo()
	{
		cout<<"name"<<this->a_name<<"num:"<<this->a_num<
	}
 
	Animal &AgeAdd()
	{
		this->a_age+=1;
		return *this;   //a2.AgeAdd().AgeAdd().AgeAdd()
	}
};
 
void test01()
{
	Animal a1;
	a1.a_num=34;
	a1.a_name="yanao";
	a1.a_age=5;
	a1.Animallnfo();       //this------->a1
 
	Animal a2("sheep");
	a2.Animallnfo();        //this-------->a2
}
void test02()
{
	Animal a3;
	a3.AgeAdd().AgeAdd().AgeAdd().AgeAdd();
	cout<<"age:"<
}
 
int main(int argc, char *argv[])
{
	test02();
 
	return 0;
}

（5）this指针的作用:

1）区分成员属性与参数(属性与参数重名)

2）成员函数需要返回对象本身时，需要使用this(实现链式编程思想)