[数据结构与算法]学习笔记：隐式构造

?隐式构造函数

//?C++?中存在隐式构造的现象：某些情况下，会隐式调用单参数的构造函数

// 隐式构造函数
// C++ 中存在隐式构造的现象：某些情况下，会隐式调用单参数的构造函数
#include <iostream>
#include <cstring>
using namespace std;
class  Person
{
private:
    int m_age;
public:
     
     Person(/* args */)
    {
        cout << "Persion() -" << this << endl;
    }
    Person(int age) :m_age(age)
    {
        cout << "Persion(int) -" << this << endl;
    }
    ~ Person(){
        cout << "~ Persion() -" << this << endl;
    }
    void display() {
        cout << "display() gae is " << m_age <<endl;
    }
};

void test1(Person Person){}
Person test2(){
    return 30;
}
int main(){
    cout << "test 1:"<< endl;
    Person p1 = 20;
    cout << "test 2:"<< endl;
    Person p2(20);
    cout << "test 3:"<< endl;
    test1(30);
    cout << "test 4:"<< endl;
    test2();
    cout << "test 5:"<< endl;
    getchar();
    return 0;
}
//结果
test 1:
Persion(int) -0x61fe04
test 2:
Persion(int) -0x61fe00
test 3:
Persion(int) -0x61fe08
~ Persion() -0x61fe08
test 4:
Persion(int) -0x61fe0c
~ Persion() -0x61fe0c
test 5:

~ Persion() -0x61fe00
~ Persion() -0x61fe04

避免隐式构造：添加explicit关键字

class  Person
{
private:
    int m_age;
public:
     
     Person()
    {
        cout << "Persion() -" << this << endl;
    }
    explicit Person(int age) :m_age(age)
    {
        cout << "Persion(int) -" << this << endl;
    }
    ~ Person(){
        cout << "~ Persion() -" << this << endl;
    }
    void display() {
        cout << "display() gae is " << m_age <<endl;
    }
};

void test1(Person Person){}
Person test2(){
    return Person(70);
}
int main(){
    cout << "test 1:"<< endl;
    Person p1 = Person(40);
    cout << "test 2:"<< endl;
    Person p2(50);
    cout << "test 3:"<< endl;
    test1(Person(60));
    cout << "test 4:"<< endl;
    test2();
    cout << "test 5:"<< endl;
    getchar();
    return 0;
}
// 结果
test 1:
Persion(int) -0x61fe04
test 2:
Persion(int) -0x61fe00
test 3:
Persion(int) -0x61fe08
~ Persion() -0x61fe08
test 4:
Persion(int) -0x61fe0c
~ Persion() -0x61fe0c
test 5:

~ Persion() -0x61fe00
~ Persion() -0x61fe04