Question

Imagine you are implementing a List Data Type in C++. This List of yours will keep items in a simple array and will hold instances of type: “Animal”.

So for example, addItem method will be something like this:

void MyAnimalList::insertAnimal(Animal a){
    animalArray[currentPosition] = a;
    currentPosition++;
 }

So we simply have a currentPosition in the our List implementation and when we add a new Animal to it, Animal a is now referenced in the animalArray in “currentPosition” and currentPosition is then increased.

My question will be about retrieveItem. Is there any difference between these 2:

void MyAnimalList::getTheLastAddedAnimal(Animal &a){
    a = animalArray[currentPosition-1];
}

Animal MyAnimalList::getTheLastAddedAnimal(){
    return animalArray[currentPosition-1];
}

Obviously, the second method will be called like:

Animal lastAddedAnimal = myAnimalList.getTheLastAddedAnimal();

and the first one should be called like:

Animal someAnimal;
myAnimalList.getTheLastAddedAnimal(someAnimal);

Answer 1

The difference is semantic. If a method is called getXXXXX, you expect it to return that thing.

Most decent compilers implement NRVO, so efficiency isn’t really an issue here. I’d go with the second version.

I would however change the definition of insertAnimal(Animal a) to insertAnimal(const Animal& a).