Run, RunLoop, Run
Put simply, a run loop is a messaging mechanism, used for asynchronous or interthread communication. It can be seen as a post box that waits for messages and delivers them to recipients.
A run loop does two things:
- wait until something happens (e.g., a message arrives),
- dispatch that message to its receiver.
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The most important feature of CFRunLoop is the CFRunLoopModes. CFRunLoop works with a system of “Run Loop Sources”. Sources are registered on a run loop for one or several modes, and the run loop itself is made to run in a given mode. When an event arrives on a source, it is only handled by the run loop if the source mode matches the run loop current mode.
1. Write an event-handling loop: it waits for events—user input, timers, etc—and calls the handlers registered for those events.
2. Put the loop in an opaque box. That’s a run loop object.
I imagine it as a jack-in-the-box. You turn the crank and calls to event handlers pop out.
