how to call a method of multiple arguments with delay

Question

I'm trying to call a method after some delay.

I know there is a solution for that:

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

I saw this question and Documentation

But my question is: How can I call a method that takes two parameters??

for instance:

- (void) MoveSomethigFrom:(id)from To:(id)to;

How would I call this method with delay, using performSelector:withObject:afterDelay:

Thanks

Solution 1

use dispatch_after:

double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    //code to be executed on the main queue after delay
    [self MoveSomethingFrom:from To:to];
});

EDIT 2015: For Swift, i recommend using this small helper method: dispatch_after - GCD in swift?

Solution 2

You can also implement method in NSObject's category using NSInvocation object (works in all versions of iOS). I guess it should be something like this:

@interface NSObject(DelayedPerform)

- (void)performSelector:(SEL)aSelector withObject:(id)argument0 withObject:(id)argument1  afterDelay:(NSTimeInterval)delay {

  NSMethodSignature *signature = [self methodSignatureForSelector:aSelector];

  NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
  [invocation setTarget:self];
  [invocation setSelector:aSelector];
  [invocation setArgument:&argument0 atIndex:2];
  [invocation setArgument:&argument1 atIndex:3];

  [invocation performSelector:@selector(invoke) withObject:nil afterDelay:delay];

}

@end

Solution 3

Other ideas:

1) You could use NSInvocations:

+ (NSInvocation *)invocationWithMethodSignature:(NSMethodSignature *)signature
(>> see Eldar Markov's answer)

Documentation:
https://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSInvocation_Class/Reference/Reference.html

2) You could use a helper method..

[self performSelector:@selector(helperMethod) withObject:nil afterDelay:delay];

- (void) helperMethod
{
    // of course x1 and x2 have to be safed somewhere else
    [object moveSomethigFrom: x1 to: x2];
}

3) You could use an array or a dictionary as parameter..

NSArray* array = [NSArray arrayWithObjects: x1, x2, nil];
[self performSelector:@selector(handleArray:) withObject:array afterDelay:delay];

- (void) handleArray: (NSArray*) array
{
    [object moveSomethigFrom: [array objectAtIndex: 0] to: [array objectAtIndex: 1]];
}

Solution 4

Swift:

    let delayInSeconds = 3.0;
    let delay = delayInSeconds * Double(NSEC_PER_SEC)
    let popTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay));
    dispatch_after(popTime, dispatch_get_main_queue(), {
        // DO SOMETHING AFTER 3 sec
    });

Solution 5

Here is how you can trigger a block after a delay in Swift:

runThisAfterDelay(seconds: 5) { () -> () in
    print("Prints this 5 seconds later in main queue")
    //Or perform your selector here
}

/// EZSwiftExtensions
func runThisAfterDelay(seconds seconds: Double, after: () -> ()) {
    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(seconds * Double(NSEC_PER_SEC)))
    dispatch_after(time, dispatch_get_main_queue(), after)
}

The argument count does not really matter.

Its included as a standard function in my repo: https://github.com/goktugyil/EZSwiftExtensions

View more solutions

Comments

[Alexander]

Either that, or you can put as many parameters as you want in a container and send it as an argument for the performSelector: withObject: afterDelay method.

[Eldar Markov]

you can use it in >= 3.2 as well. I just wanted to show that it's not necessary to use GCD. I'll edit my original answer)

[Frade]

Ok.. I'm sorry but, what is GCD? what's the problem using it?

[Frade]

I'm asking, because I have three answers and the 3 are good. Just trying to understand which is the best one to use. Thanks

[Eldar Markov]

GCD - it's Grand Central Dispatch. Part of iOS sdk 4.0 and higher.If you want to use it in all versions of iOS use mine version)

[Frade]

This seems a good approach, it really delays the call. But it happens something strange, the method doesn't do what is expected, does something else, that I can't even understand..

[Frade]

got it.. It was some code that was executed during the delay.. thanks

[Martin Ullrich]

Yes if you really want to deploy on devices < 4.0 you have to stay away from GCD. But developing for iOS 4+ is safe as over 90% of active devices are running it and testing/coding effort is heavily reduced (assuming that you do serious testing)

[Martin Ullrich]

additionally, GCD improves code readability because because you don't have to have lots of methods being called asynchronously (you "just" have to get used to ^{}-Notations)

[ArtOfWarfare]

As a suggestion, don't reference other answers on SO as being "above" or "below", as they can be sorted more ways than one, and that most people sort by rating, which can be volatile. I suggest hitting the "share" button beneath the answer and sharing a link to it, for incase a question ends up with a large number of answers.

[vir us]

is there a way to cancel scheduled call?

[vir us]

if someone is interested this should work to cancel scheduled call (if performSelector:withObject:afterDelay: was used): [NSObject cancelPreviousPerformRequestsWithTarget:yourTarget selector:aSelector object: anArgument];

[Martin Ullrich]

@iEngineer: Sure u got everything right? i once used "MSEC_PER_SEC" instead of "NSEC_PER_SEC" which is 10^6 times faster.