Creating a Blueprint Interface for pickup objects

To create a Blueprint Interface, follow the given steps:

1. Right-click in your project's Blueprints directory, and select Create Advanced Asset | Blueprints | Blueprint Interface:

2. Name it BPI_PickupActor.

When you open it up, you'll see that it contains a Functions list, and nothing else. You'll notice that the graph can't be edited. This is because the interface is simply a list of functions that the attached object must implement, but those functions don't get written in the interface.

3. By default, it's created a new function declaration for you. Name it Pickup.
4. Under the function's Details | Inputs, add a new input. Set its type to Scene Component | Object Reference, and name it AttachTo:

5. Add another function, and call it Drop. This one doesn't need any input.
6. Compile, save, and...