CODEWITHSUNDEEP
classpointersc++11referencervalue-reference
Nick
Nick

Reputation: 10539

C++11 rvalue references vs references vs pointers vs "normal" members

I have code like this:

class A{
};

class B{
   B(A &&a) : a(std::move(a)){};
   A a;
}

A a{};
B b{ std::move(a) };
// a is unusable

I use rvalue, because I do not want object to be copy-ed.

I am thinking of changing the class B to use references:

class A{
};

class B{
   B(A &a) : a(a){};
   A &a;
}

A a{};
B b{ a };
// a is usable

Will there be any negative effects of this, except live-time concerns? I do not reassign the a object, so I do not need pointers. but should I consider them?

Upvotes: 0

Views: 166

Answers (1)

aschepler
aschepler

Reputation: 72356

Why not let the caller decide whether to move or copy its A object?

class A {};

class B {
public:
    B(A a_param) : a(std::move(a_param)) {}
private:
    A a;
};

void f1() {
    A a;
    B b{a}; // Makes a copy, a is still usable.
}

void f2() {
    A a;
    B b{std::move(a)}; // Does a move, a is not usable.
}

void f3() {
    B b{A{}}; // Does a move of the temporary object.
}

Upvotes: 1

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