How to cout a constructor?

Question

I'm kinda new to C++ and i got this problem while learning about it

So I have created this class

class A {
    int num;
public:
    //constructor
    A(int num) {
        this->num = num;
    }
    int getNum() {
        return num;
    }
    //overload <<
    friend ostream& operator << (ostream& os,A& a) {
        os << a.getNum();
        return os;
    }
};

In the main function, if I use cout<< A(1); it compiles wrong ( code C2679 in Visual Studio 2017 ).
How can I make it like cout<< int(1); ? Do I need to overload any other operator?

Possible duplicate of [How come a non-const reference cannot bind to a temporary object?](https://stackoverflow.com/questions/1565600/how-come-a-non-const-reference-cannot-bind-to-a-temporary-object) — Artyer, May 07 '19 at 10:28

score 4 · Accepted Answer · answered May 07 '19 at 10:26

4

Your overload needs to take a const A&, otherwise the anonymous temporary A(1) cannot bind to it.

answered May 07 '19 at 10:26

Bathsheba

231,907
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Thanks a lot, I did it – Cường Lê May 07 '19 at 10:32

score 1 · Answer 2 · answered May 07 '19 at 14:34

1

One more way is to overload the operator << with rvalue references

friend ostream& operator << (ostream& os, A&& a) {        
        os << a.getNum();
        return os;
    }

answered May 07 '19 at 14:34

nayab

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How to cout a constructor?

2 Answers2