how does one do Inter-Object communications (e.g. triggering events)

How does one do Inter-Object communications (e.g. triggering events) in Corona? Some sample code would be great.

Notes:

* I see there is a way to create custom events on an object, however it seems you really need a handle to that object before you can trigger (dispatch) it.

* What I’m interested here is two completely separate objects. Eg say you clicked on a display object on the screen the ability to say in a global event type sense “MyInventoryHasIncreased”, and then have any other display objects that need to subscribe to this pick it up and adjust their display accordingly.

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