Question

I’m tring to learn C++ and I have a little problem. I have some instances of Foo class. And I have a FooContainer with vector<Foo> data with a method

void FooContainer::add(Foo item) {
    this->data.push_back(item)
}

I want FooContainer to be the real holder of Foo elements. I don’t understand what is the better way to pass the items from main to Foo.

In my main I have:

Foo item(...);
container.add(item);

In this way I have an object allocated in main, and I pass a copy to the container. I have the element existing in 2 place, so I have to delete the one in the main after all add().

Or is better to have a pointer in the main, construct the item with new keyword, and pass the pointer? And in this way Container.data should be a vector<Foo*>?

Or, again, have the element in main, add in the container by reference, and not delete it in main?

I’m a bit confused.

EDIT

for educational purpose i don’t want to use c++11 or boost shared pointer: my ideas are confused on pointer and reference and basic things, before pass into advanced argument (even if more elegant) i want to have clear basis of what i am doing!

Answer 1

It all depends on your need.

If all your instances are Foo [and not a subclass of Foo], IMO using vector<Foo> is simpler and thus should be preferred.

However, if you have a class Bar which extends Foo, trying to add it to your vector will cause object slicing, and your program will behave not as expected. In this case, you should prefer vector<Foo*>

So, as I started – it all depends on the specific need, but the last point must be considered if you plan on extending Foo.