Delay a method call in objective-c

Question

I know this can be done by using:

[self performSelector:@selector(myMethod) withObject:nil afterDelay:3.0]

However, the problem is that I want only 1 method call do be done. With this function the calls will stack on top of each other. I want to make a call and if another call is made the first one will be dismissed. Ideas?

Answer 1

Once the method is executing then there is no way of stopping it.

But you can cancel if it is not fired. You can do something like this

//.... your code
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(myMethod) object:nil];
[self performSelector:@selector(myMethod) withObject:nil afterDelay:3.0];
//.... your code

In this way you can cancel previous perform request only if the myMethod is not being fired.

Answer 2

In the Code Snippet Library in Xcode you can find one called GCD: Dispatch After, which looks like this:

double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    <#code to be executed on the main queue after delay#>
});

Pretty self-explanatory.