Summary:
The purpose of `EventBeat` is handling an asynchronous callback to itself which is being delivered on some different thread. That brings a challenge of ensuring that the `EventBeat` object stays valid during the timeframe of callback execution. The concept of Owner helps with that.
The owner is a shared pointer that retains (probably indirectly) the `EventBeat` object. To ensure the correctness of the call, `EventBeat` retains the owner (practically creating a retain cycle) during executing the callback. In case if the pointer to the owner already null, `EventBeat` skips executing the callback.
It's impossible to retain itself directly or refer to the shared pointer to itself from a constructor. `OwnerBox` is designed to work around this issue; it allows to store the pointer later, right after the creation of some other object that owns an `EventBeat`.
Reviewed By: JoshuaGross
Differential Revision: D17128549
fbshipit-source-id: 7ed34fd865430975157fd362f51c4a3d64214430
Summary: We don't use it anymore. (And that was debug only concept.)
Reviewed By: sammy-SC
Differential Revision: D17115538
fbshipit-source-id: 20aac5457e37666cbf9ca9f62cdfca411026c219
Summary: That's bummer that we have to do it, but it's actually reasonable. Files in `core` and `events` depend on each other creating circular dependencies and other similar hard problem.
Reviewed By: mdvacca
Differential Revision: D14195022
fbshipit-source-id: 96a44ae28631cc9ccd7d7de72a94526f9e0dd12a
Valentin Shergin