NSOperationQueue mainQueue vs performSelectorOnMainThread?

ios iphone objective-c concurrency nsoperationqueue
ma11hew28 picture ma11hew28 · May 9, 2012 · Viewed 10.1k times · Source

What's the difference between this:

[[NSOperationQueue mainQueue] addOperationWithBlock:^{
    [self doSomthing:object];
}];

and this:

[self performSelectorOnMainThread:@selector(doSomething:) withObject:object waitUntilDone:NO]

Answer

Mike Z picture Mike Z · May 9, 2012 
[self performSelectorOnMainThread:@selector(doSomething:) 
                       withObject:object 
                    waitUntilDone:NO]

Will perform the selector right when it is called. This is what you have to use if you want to affect the UI from a background thread. If you say YES to waitUntilDone it will block the thread until the method has completed.

mainQueue adds that block to the operation queue of the mainthread but does not guarantee when it will be executed. There could be other items in that queue still waiting to execute.

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