Objective-C @Selector(methodWithArguments)

Question

Possible Duplicate:
Arguments in @selector

This is probably a really simple question, but I need a really good answer...

Using the following code I can call a method when a button is clicked...

[pushButton addTarget:self action:@selector(pushOrPull:andVI:) forControlEvents:UIControlEventTouchUpInside];
[pullButton addTarget:self action:@selector(pushOrPull:andVI:) forControlEvents:UIControlEventTouchUpInside];

The method is below...

-(void) pushOrPull: (int)pushPull andVI: (NSString *) videoId {

}

I want the buttons to be able to supply arguments to that method, but when I try this...

[pushButton addTarget:self action:@selector(pushOrPull:2 andVI:@"someVID") forControlEvents:UIControlEventTouchUpInside];
[pullButton addTarget:self action:@selector(pushOrPull:1 andVI:@"someVID") forControlEvents:UIControlEventTouchUpInside];

Xcode gives me two errors: "expected )"

How can I supply these two arguments to the method when my buttons get tapped?

@Almo No that is not a duplicate buttons cannot be timed! I have no clue when the user will tap a button? — The Man, Jul 17 '12 at 15:22
Well is there any way that I can call a method (with arguments) on a button tap? — The Man, Jul 17 '12 at 15:24
Does Shane's answer here (http://stackoverflow.com/questions/1018195/objective-c-calling-selectors-with-multiple-arguments) not solve your problem? — tarheel, Jul 17 '12 at 15:26
You can't use the NSInvokation? That was the important part of the dupe; not the timer. If I have this wrong, then my apologies. — Almo, Jul 17 '12 at 15:27
possible duplicates: [How can I send two arguments in a selector method?](http://stackoverflow.com/questions/1857817/how-can-i-send-two-arguments-in-a-selector-method?rq=1), [How to pass data through selector upon custom button click?](http://stackoverflow.com/questions/9918273/how-to-pass-data-through-selector-upon-custom-button-click?rq=1) — jscs, Jul 17 '12 at 16:40

score 1 · Answer 1 · answered Jul 17 '12 at 15:22

Unfortunately, you can't. Buttons only "know how" to send themselves as the first argument. The best bet is to have the buttons "belong" to some view controller (to which they send their events) which can interpret the button press, and then call a delegate method elsewhere with as many arguments as you need.

To answer a related question, a "selector" never carries actual arguments, but it does carry one colon per argument: @selector(aMethodWithThis:andThat:)

glenn sayers · Accepted Answer · 2012-07-17T15:49:25.020

What you could do is just have a method in the middle.

[pushButton addTarget:self action:@selector(runMyMethod) forControlEvents:UIControlEventTouchUpInside];
pushButton.tag =0;
[pullButton addTarget:self action:@selector(runMyMethod) forControlEvents:UIControlEventTouchUpInside];
pullbutton.tag =1;

-(void) runMyMethod:(id)sender {
    if(sender.tag ==0)
    {
       [self pushOrPull:1 andVI:@"someVID"];
    }
    else if (sender.tag ==1)
    {
       [self pushOrPull:2 andVI:@"someVID"];
    }
}
-(void) pushOrPull: (int)pushPull andVI: (NSString *) videoId {

}

Patrick Perini · Answer 3 · 2012-07-17T15:32:11.913

0

This is a bit better:

// set up an NSMutableDictionary, videoIDsForButtons as an iVar or property
[pushButton addTarget:self action:@selector(buttonWasPressed:) forControlEvents:UIControlEventTouchUpInside];
[videoIDsForButtons setObject: @"someVID" forKey: pushButton];

[pullButton addTarget:self action:@selector(buttonWasPressed:) forControlEvents:UIControlEventTouchUpInside];
[videoIDsForButtons setObject: @"someVID" forKey: pullButton];

- (void)buttonWasPressed:(id)sender
{
    if (sender == pushButton)
    {
        [self pushOrPull: 2 andVI: [videoIDsForButtons objectForKey: sender]];
    }
    else // assume pullButton
    {
        [self pushOrPull: 1 andVI: [videoIDsForButtons objectForKey: sender]];
    }
}

This is because selectors don't take arguments, only method calls do. And when a button is pressed, it supplies itself as the only argument (sender). You should have a whole separate responder method that looks at sender and determines the appropriate recourse.

edited Jul 17 '12 at 15:32

answered Jul 17 '12 at 15:27

Patrick Perini

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Thanks, but question: can I do something like this before I call the selector method... pushButton.videoID = @"someVID"; .... And then reference that in the buttonWasPressed Method? – The Man Jul 17 '12 at 15:29
Ah. Well, you could subclass the button, but that's a bit much. I'll provide an alternative if my sample. – Patrick Perini Jul 17 '12 at 15:30
Sorry, No I have like 20 push and pull buttons... And I am creating the selector when I create a Table View... – The Man Jul 17 '12 at 15:33
Or maybe it will still work??? – The Man Jul 17 '12 at 15:35
You're really going to have to rethink your data setup here, because selectors simply don't work like that. – Patrick Perini Jul 17 '12 at 15:36
It's a big table view :) – The Man Jul 17 '12 at 15:37
You could set the tag of the button, if that's what you're aiming for? I'll update my answer with an example. – glenn sayers Jul 17 '12 at 15:39
Are you sure you need UIButtons at all? Table view cells can be clicked without needing to be/contain buttons. – Patrick Perini Jul 17 '12 at 15:39
Yea There are two buttons in each table view cell – The Man Jul 17 '12 at 15:40
Yea can you update your answer with tags... – The Man Jul 17 '12 at 15:45

score 0 · Answer 4 · answered Jul 17 '12 at 15:40

unfortunately the -addTarget:action:forControlEvents: can call back you via the following method with the next parameters only:

-(IBAction)selector:(id)sender forEvent:(UIEvent *)event;

so, you should check inside this method which object fired the event (sender), and after it, still inside this method you can call your own -pushOrPull:andVI: method with the desired parameters, or you can set two different callback methods as well and then you won't have to check the sender parameter, just call your -pushOrPull:andVI: like this:

{
    // ...

    [pushButton addTarget:self action:@selector(pushButtonTouchedUpInside:) forControlEvents:UIControlEventTouchUpInside];
    [pullButton addTarget:self action:@selector(pullButtonTouchedUpInside:) forControlEvents:UIControlEventTouchUpInside];

    // ...

}

- (IBAction)pushButtonTouchedUpInside:(id)sender {
    [self pushOrPull:2 andVI:@"someVID"];
}

- (IBAction)pullButtonTouchedUpInside:(id)sender {
    [self pushOrPull:1 andVI:@"someVID"];
}

Objective-C @Selector(methodWithArguments)

4 Answers4