Question

What is the difference between using this

[self performSelectorOnMainThread:@selector(doStuff:) 
                       withObject:myObject 
                    waitUntilDone:YES];

instead of simply

[self doStuff:myObject];

in terms of CPU load? Or there are any other advantages?

thanks.

Answer 1

[self performSelectorOnMainThread:@selector(doStuff:) 
                   withObject:myObject 
                waitUntilDone:YES];

This makes sure that the selector is performed on the main thread by adding it to the main run loop. When you set waitUntilDone:YES, you will let your current thread idle as long as the main run loop needs to perform the selector.
In a single threaded environment this will let the runloop run right after you called this, in a multithreaded environment, the main runloop will perform the selector once it does the next step.

You have in any of the both cases a small overhead as the selector isn’t performed right after you called the function but at a later point while [self doStuff:myObject]; performs the selector immediately