IPhone performSelector issue

问题

I have working code: [self performSelector:@selector(doSomething) ];

but when I change this line to:

[self performSelector:@selector(doSomething) withObject:nil afterDelay:1.0];

it reports error - unrecognized selector....

could you tell me what is the problem in?

thank you

回答1:

If you changed your method to take an object parameter then you need to change the @selector() argument to include the ":", e.g., @selector( doSomething: )

This works:

- (void) foo
{
    NSLog(@"foo!");
}


- (void)applicationDidFinishLaunching:(NSNotification *)aNotification 
{        
    [self performSelector: @selector(foo) withObject: nil afterDelay: 0.1];
}

So you can pass a selector that takes no param to performSelector:withObject:afterDelay: and I presume it ignores the withObject: param which I wasn't 100% sure of.

回答2:

It looks like your problem is that your selector is doSomething and not doSomething:. Without the :, there's nowhere in the message to insert an object, even nil.

回答3:

Is self still around? You could be trying to send a message to an NSZombie.

来源：https://stackoverflow.com/questions/3126421/iphone-performselector-issue