CODEWITHSUNDEEP
c++constructorreturnreturn-type
the individual
the individual

Reputation: 55

Return type of a constructor in c++

I am learning c++, and I came across following code segment:

class X
{
    int i;

public:
    X(int ii = 0);

    void modify();
};

X::X(int ii)
{ i = ii; }

void X::modify()
{ i++; }

X f5()
{ return X(); }

const X f6()
{ return X(); }

void f7(X& x) // Pass by non-const reference
{ x.modify(); }

int main()
{
    f5() = X(1);
    f5().modify();
}

I am stuck particularly in this segment-

X f5()
{ return X(); }

Does this part of code return an object of type x by value? Can a constructor return an object?

Upvotes: 0

Views: 2468

Answers (3)

ANjaNA
ANjaNA

Reputation: 1426

simple, you misunderstand the constructor of the class and a function. your class class X have a constructor and it is X(int ii = 0);.

X f5() is not a constructor. Clearly understand that first.

Constructor of a class should have the same name as class and have no a return value. It does,t make any sense. (read further about class and constructor)

X f5() {
  return X();
}

This is a function which returns a X type of object. it returns the X().

X() creates a value-initialized temporary object of type X.

Upvotes: 1

Mike Seymour
Mike Seymour

Reputation: 254771

Does this part of code returns an object of type x by value?

Yes, it creates and value-initialises a temporary object of type X (by calling the constructor with the default value of zero) and returns that.

can a constructor can return an object?

No, that doesn't make any sense. But an conversion expression like X() does.

Upvotes: 4

ForEveR
ForEveR

Reputation: 55897

f5 is just function, not constructor. And it returns constructed object of type X.

Upvotes: 3

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