I'm trying to find a good example of adding a capability to an item using the AttachCapabilityEvent. Does anyone know of any examples or repos or tutorials for creating and adding a basic capability to an ItemEntity? I'm wandering around right now trying to find what specifically I need to do and why. Thank you!

On the FCW wiki, there is a doc about capabilities and an example for it. The official docs still need to be refactored, hence the redirection to the wiki itself.

I will add on an extra note that the generic event must have 'Entity' as the type as generic events are fired on the exact type and not any subtypes. Therefore, if you only want to apply your capability to an ItemEntity, just do an instanceof cast or directly check the EntityType.

Okay awesome, I'll give that a read!

For the second part, are you saying something like this wouldn't work and I should use the second code?
 

    // What I have now
    @SubscribeEvent
    public static void handle(AttachCapabilitiesEvent<ItemStack> event) {
        // Code here
    }
      
    // instanceof cast
    public static void handle(AttachCapabilitiesEvent<Entity> event) {
        if(event.getObject() instanceof ItemStack){
          ItemStack stack = (ItemStack) event.getObject();
        }
    }
      
      

 

The getObject() associated the Entity might be an ItemEntity, it will never be an ItemStack.

Awesome, thanks!
I am noticing that when I run the code 

@SubscribeEvent
    public static void handle(AttachCapabilitiesEvent<ItemStack> event) {
        LOGGER.info("ItemStack: ", event.getObject().getDisplayName());
    }

It does successfully print out all of the item stacks in the area. I am running into issues in actually attaching the capabilities to this ItemStack though.

Are you trying to attach the capability to the item stack or the entity? If the ItemStack, then you would use the method you are currently showing with the method within the event itself (event#addCapability)