完美转发

Posted 2020-08-14 韵切

完美转发

#include <iostream>
#include <string>
#include <utility>

using std::cout;
using std::endl;
using std::string;

class  Name
{
public:
    Name(const string & aName) :name{aName}
    {
        cout << "Lvalue Name constructor." << endl;
    }

    Name(string && aName) :name{ std::move(aName) }
    {
        cout << "Rvalue Name constructor." << endl;
    }
    
    const string & GetNmae()const
    {
        return name;
    }

private:
    string name;

};


class Person
{
public:
    template<typename T1,typename T2>
    Person(T1 && first, T2 && second) :firstname{ std::forward<T1>(first) }, seondname{ std::forward<T2>(second) }
    {
        cout << "-------------------" << endl;
    }

    string getName()const
    {
        return firstname.GetNmae() + " " + seondname.GetNmae();
    }

private:
    Name firstname;
    Name seondname;
};

int main()
{
    Person me{ string{"Ivor"},string{"Horton"} };
    cout << me.getName() << endl << endl;

    string first{"Fred"};
    string second{"Fernackerpan"};
    Person other{first,second};
    cout << other.getName()<< endl << endl;

    Person brother{ first,string{"Bloggs"} };
    cout << brother.getName() << endl << endl;

    Person another{"Richard","Horton"};
    cout << another.getName() << endl;
}

输出结果：

Rvalue Name constructor.
Rvalue Name constructor.
-------------------
Ivor Horton

Lvalue Name constructor.
Lvalue Name constructor.
-------------------
Fred Fernackerpan

Lvalue Name constructor.
Rvalue Name constructor.
-------------------
Fred Bloggs

Rvalue Name constructor.
Rvalue Name constructor.
-------------------
Richard Horton