Using a constructor for return

Question

Just a quick question.

I've written some code that returns a custom class Command, and the code I've written seems to work fine. I was wondering if there are any reasons that I shouldn't be doing it this way. It's something like this:

Command Behavior::getCommand ()
{
  char input = 'x';

  return Command (input, -1, -1);
}

Anyway, I read that constructors aren't meant to have a return value, but this works in g++.

Thanks for any advice,

Rhys

Answer 1

The constructor itself doesn't have a return value. What this does is constructs a temporary Command object and returns the constructed objet to the caller. It's effectively the same as if you said:

Command temp(input, -1, -1);
return temp;

It will work on any C++ compiler.

Answer 2

getCommand isn't a constructor. The above is perfectly valid, and also generally efficient, due to thre return-value optimisation (RVO), which (I think) wouldn't apply if you instantiated a local variable and returned that.