deep copy vs shallow copy
Deep and shallow copy is a classic interview question, and it is also a common pit. Shallow
copy: simple assignment copy operation
Deep copy: re-apply space in the heap area for copy operation
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
class Person
{
public:
Person()
{
cout << "Person的无参数构造函数调用" << endl;//无参构造函数（默认构造函数）
}
Person(int age,int height)
{
m_Age = age;
m_Height=new int(height);
cout << "Person的带参数构造函数调用" << endl;//有参构造函数
}
~Person()
{
//析构代码，将堆区开辟的数据做释放操作
if (m_Height != NULL)
{
delete m_Height;
m_Height = NULL;
}
cout << "Person的析构函数调用" << endl;
}
//自己实现拷贝构造函数，解决浅拷贝带来的问题
Person(const Person &p)
{
cout << "Person拷贝构造函数调用" << endl;
m_Age = p.m_Age;
//m_Height=p.m_Height;编译器默认实现就是这行代码
m_Height = new int(*p.m_Height);
}
int m_Age;
int* m_Height;
};
void test01()
{
Person p1(18,160);
cout << "p1的年龄为：" << p1.m_Age << "身高为：" << *p1.m_Height << endl;
Person p2(p1);
cout << "p1的年龄为：" << p2.m_Age << "身高为：" << *p2.m_Height << endl;
}
int main()
{
test01();
system("pause");
return 0;
}
initialization list
Role:
C++ provides an initialization list syntax for initializing attributes Syntax
: Constructor (): attribute 1 (value 1), attribute 2 (value 2)...{}
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
class Person
{
public:
Person(int a,int b,int c):m_A(a), m_B(b),m_C(c)
{
}
int m_A;
int m_B;
int m_C;
};
int main()
{
Person p(10,20,30);
cout << p.m_A << p.m_B << p.m_C << endl;
system("pause");
return 0;
}
class object as class member
A member in a C++ class can be an object of another class. We call this member an object member.
In class B, there is object A as a member, and A is an object member.
Problem: When creating a B object, the construction and destruction of A and B Who comes first in order?
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
#include<string>
class Phone
{
public:
Phone(string pName)
{
m_PName = pName;
cout << "Phone的构造函数调用" << endl;
}
~Phone()
{
cout << "Phone的析构函数调用" << endl;
}
string m_PName;
};
class Person
{
public:
//Phone m_Phone=pName; 隐式转换法
Person(string name, string pName):m_Name(name),m_Phone(pName)
{
cout << "Person的构造函数调用" << endl;
}
~Person()
{
cout << "Person的析构函数调用" << endl;
}
string m_Name;
Phone m_Phone;
};
//当其他类对象作为本类成员，构造时候先构造类对象，再构造自身。
//析构的顺序与构造相反
void test01()
{
Person p("张三", "苹果XR");
cout << p.m_Name << "拿着" << p.m_Phone.m_PName << endl;
}
int main()
{
test01();
system("pause");
return 0;
}
static member variable
A static member is to add the keyword static before the member variable and member function, which is called a static variable.
Static members are divided into:
static member variable
All objects share a piece of data
Allocate memory during compilation
In-class declaration, out-of-class initialization
#include<iostream>
using namespace std;
class Person
{
public:
//1、所有对象都共享同一份数据
//2、在编译阶段分配内存
//3/类内声明，类外初始化
static int m_A;
};
int Person::m_A = 100;
void test01()
{
Person p;
cout << p.m_A << endl;
Person p2;
p.m_A = 200;
cout << p.m_A << endl;
}
int main()
{
test01();
system("pause");
return 0;
}
#include<iostream>
using namespace std;
class Person
{
public:
//1、所有对象都共享同一份数据
//2、在编译阶段分配内存
//3/类内声明，类外初始化
Person()
{
}
static int m_A;
//静态成员变量也是有访问权限的
private:
static int m_B;
};
int Person::m_A = 100;
int Person::m_B = 200;
void test01()
{
Person p;
cout << p.m_A << endl;
Person p2;
p.m_A = 200;
cout << p.m_A << endl;
}
void test02()
{
//静态成员变量不属于某个对象上，所有对象都共享同一份数据
//因此静态成员变量有两种访问方式
//1、通过对象进行访问
//Person p;
//cout << p.m_A << endl;
//2、通过类名进行访问
cout << Person::m_A << endl;
//cout << Person::m_B << endl;//无法访问
}
int main()
{
//test01();
test02();
system("pause");
return 0;
}
static member function
All objects share a function
Static member functions can only access static member variables
#include<iostream>
using namespace std;
class Person
{
public:
Person()
{
}
static void func()
{
m_A = 100;//静态的成员函数可以访问静态成员变量
//m_B = 100;//静态成员函数不可以访问非静态成员变量
cout << "static void func调用" << endl;
}
static int m_A;
int m_B;
private:
static void fun2()
{
cout << "static void func2调用" << endl;
}
};
int Person::m_A = 100;
void test01()
{
//1、通过对象访问
Person p;
p.func();
//2、通过类名访问
Person::func();
//Person::func2();//类外访问不到私有的静态成员函数
}
int main()
{
test01();
system("pause");
return 0;
}