How to return a class member vector in c++11

c++, c++11, std

Solution

//1 - classic way?
void GetVect(std::vector<int>& v)
  {
     v = vect;// assignment with swap?
  }

This is just plain ugly, you still need a copy and you make your interface too complex.

//2 - RVO?
std::vector<int> GetVect()
  {
    return vect;
  } 

//3 - RVO with const?
std::vector<int> GetVect() const
  {
    return vect;
  }

Functionally the same, but you likely want 3 to indicate that `getVect` does not change your class state so `const` semantics can be applied correctly.

//4 - just move?
std::vector<int> GetVect() 
  {
    return std::move(vect);
  }  

It seems very unlikely you want this, after calling `GetVect` the internal `vect` will no longer contain any elements.

 //5 - move with {}?
std::vector<int> GetVect() 
  {
    return { std::move(vect) };
  }  

This should end up being the same as 4, you just call the return object's move constructor more explicitly.

For performance what you might actually want is this:

const std::vector<int>& GetVect() const
{
    return vect;
}

This way you can read the object without the need for copying. If you want to write to the returned vector, create a copy explicitly. More details can be found in this question

Problem

Original source

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