PerformSelector with Delay 0?

Question

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How does -performSelector:withObject:afterDelay: work?

I often use this code to let the UI finish its business before calling a long-running method:

[obj performSelector:@selector(go) withObject:nil afterDelay:0];

But what does it do?

My personal interpretation has always been that the go method is called on the next run loop, but surely that's not even right.

Thanks Tom, that works. Should I remove the question (delete)? — Dan Rosenstark, Feb 05 '13 at 21:59
@Nate: They did? WTF. That was incredibly helpful when knowing whether the asker was unlikely to mark anything as answered. — Lily Ballard, Feb 05 '13 at 23:32
I'd kind of prefer that it get closed as a dupe, @Nate, because it offers different keywording than the other question. Otherwise i'd just delete it. — Dan Rosenstark, Feb 06 '13 at 06:22

Lily Ballard · Answer 1 · 2013-02-05T22:17:14.820

Calling it with delay 0 will indeed invoke this method on the next pass through the runloop.

IIRC, what it does is set up a struct that represents the target and action, and attach a CFRunLoopSource to the runloop that, when triggered, will invoke the action on the target. It then signals the runloop to tell it that it has a ready source. This means that the next time the runloop processes its sources (i.e. the next pass through the runloop), it will perform your delayed selector.

PerformSelector with Delay 0?

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