预置与弃置函数

#include <iostream>
using namespace std;

class B;

class B{
public:
    B();
    B(string _str):str(_str){}
    ~B(){
        cout<<"delete B  str = "<<str<<endl;
    }

private:
    string str;
public:
    string getStr() const {return str;}
};

class A{
public:
    A() = default;
    A(string _str):str(_str){}
    ~A(){
        cout<<"delete A str = "<<str<<endl;
    }

    void test() = delete; //禁止使用
    
private:
    string str;

public:
    void printfStr(){
        cout<<str<<endl;
    }

    A& operator= (const A&) = delete; // 禁止使用 = 进行拷贝

    A& operator= (const B& b){
        this->str = b.getStr();
        return *this;
    }
};

int main()
{
    A *a = new A; //如果A()后面没有 = default则编译报错
    delete a;

    A a1("a1");
    A a2("a2");
    //a2.test();  编译报错  test已弃用

    //a1 = a2; 编译报错
    B b("b1");
    a2 = b;
    a2.printfStr();
    return 0;
}