Question

In the following code, is it really bad practice for updateWithContex to return the same object it took as a parameter?

class SomeClass{
   Foo updateWithContex(Foo foo){
       foo.setAppId(i);
       foo.setXId(index);
       //.....
       return foo;
   }
}

class Foo{

    public void setAppId(int appId)
    {
       //
    }
    public void setXId(int appId)
    {
        //
    }
    public void changeState(X x)
    {
       //
    }
}

In C++ , I have seen code like this:

 BigObject&
   fastTransform( BigObject& myBO )
   {
      // When entering fastTransform(), myBO is the same object as the function
      // argument provided by the user. -> No copy-constructor is executed.
      // Transform myBO in some way
      return myBO;   // Transformed myBO is returned to the user.
   }

Is this also wrong?

Answer 1

Returning an object will suggest to users of your API that the passed in object will not be changed and a new modified object returned instead. To make it clear that this is not the case I would suggest changing the return type to void.