Signals & Hooks

Signals

DocumentService provides 5 signals: UpdatedSignal, OpenedSignal, ReadSignal, ClosedSignal, CacheChangedSignal.

These signals allow you to wait for a document to be open before modifying it or to tap into cache changes (e.g. for replication), for example. They also implement the Once and cancellation functionality of after hooks, through :Once and :Disconnect.

They are implemented with sleitnick signals, so listeners are wrapped in a task.spawn and hence will run immediately (and before the method returns), until a yield is encountered, and will run in reverse order to the order they are added.

Hooks

Hooks are now deprecated (except for before hooks, which can be useful for debugging/logging). Use signals in new work instead.

To listen to and respond to events, like saving or reading data, DocumentService has a hooks API: HookBefore, HookAfter, OnceBefore, and OnceAfter.

Hooks run sequentially in the order they are added, and generally, should not yield.

HookBefore and HookAfter return a cancel function. This will clean up the hook and stop it from running again in response to any future events. Note that once an event happens, the sequence of hooks to run is fixed and cannot be changed for while the hooks are running for that particular event.