CODEWITHSUNDEEP
c++c++11move
user5929018
user5929018

Reputation: 201

Disabling move constructor

I would like to disable the move constructor in the class. Instead of moving, I would like to base on copy constructor. When I try to write this code:

class Boo
{
public:
    Boo(){}
    Boo(const Boo& boo) {};
    Boo(Boo&& boo) = delete;
};

Boo TakeBoo()
{
    Boo b;
    return b;
}

during compilation I received error:

error C2280: 'Boo::Boo(Boo &&)': attempting to reference a deleted function

How can I disable the move constructor and force copies instead?

Upvotes: 15

Views: 7222

Answers (2)

Niall
Niall

Reputation: 30605

Marking a function as =delete makes the function available for overload resolution, but if chosen, the compilation fails; this functionality is not limited to constructors and other special functions (see here). Previously (circa C++03) making the member private achieved a similar result.

Hence, the code as in the sample, effectively means you prohibiting the construction of an object of the class from a temporary or expiring value (rvalues) - the move constructor.

To correct this, remove the move constructor completely. In the case of the class, once a copy constructor is present (user defined), the move is implicitly not generated anyway (move constructor and move assignment operator).

class Boo
{
public:
    Boo(){}
    Boo(const Boo& boo) {};
    //Boo(Boo&& boo) = delete;
};

Upvotes: 10

Marian Spanik
Marian Spanik

Reputation: 1109

Do not create any move constructor:

class Boo
{
public:
    Boo(){}
    Boo(const Boo& boo) {};
};

The move constructor is not automatically generated as long as a user-defined copy constructor is present so the copy constructor is called.

Upvotes: 26

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