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After reading the documentation for NSRunLoop I did not understand very much. I am spawning a secondary thread that has a NSTimer in it that launch every 1sec. Which update a label on the screen with the performSelectorOnMainThread..
However to get it to work I needed a runloop but I do not understand the concept of it?
Anyone who could try to explain it?
Thanks.
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A RunLoop object processes input for sources, such as mouse and keyboard events from the window system and Port objects. A RunLoop object also processes Timer events. Your application neither creates nor explicitly manages RunLoop objects.
Run Loop is a mechanism that allows threads to process events at any time without exiting. Run Loop is actually an object that manages the events and messages that it needs to process and provides an entry function to execute the logic of the Event.
A run loop is an event processing loop that you use to schedule work and coordinate the receipt of incoming events. The purpose of a run loop is to keep your thread busy when there is work to do and put your thread to sleep when there is none. Run loop management is not entirely automatic.
The RunLoop. main uses several modes and switches to a non-default mode when user interaction occurs. However, RunLoop. main as a Combine scheduler only executes when the default mode is active. In other words, the mode is switched back to default when user interaction ends and the Combine closure executes.
A run loop is effectively:
while(... get an event ...)
... handle event ...;
It runs on a thread; the main thread has the main event loop where user events are processed and most UI drawing, etc, occurs. The documentation explains it in detail.
However, in your case, you don't need a thread.
It sounds like all you are doing is periodically updating a label in the UI; something that isn't terribly compute intensive.
Just schedule your timer in the main thread and be done with it. No need for spinning up a thread, using performSelectorOnMainThread:, or incurring all the complexities of guaranteeing data coherency across threads.
Sorry -- didn't understand your question.
Internally, a run loop works by basically putting a flag in the run loop that says "after this amount of time elapses, fire the timer". No additional threads involved and, better yet, it isn't polling to check the time. Think of a run loop as effectively maintaining a timeline. It'll passively let time elapse until there is something of interest found on the timeline (all without polling -- polling sucks. to be avoided.)
It does mean, though, that a Timer will never be 100% accurate. As well, if you have a timer repeating every second, it'll drift over time.
Also; instead of directly triggering a drawing event. Your timer should invalidate the view that needs updating, then let the underlying objects deal with when it is best to actually update the screen.
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This page explains it pretty well. FTA:
A run loop is essentially an event-processing loop running on a single thread. You register potential input sources on it, pointing it to the code that it should execute whenever input is available on those sources.
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