Passing parameters to addTarget:action:forControlEvents

I am using addTarget:action:forControlEvents like this:

[newsButton addTarget:self
action:@selector(switchToNewsDetails)
forControlEvents:UIControlEventTouchUpInside];

and I would like to pass parameters to my selector "switchToNewsDetails". The only thing I succeed in doing is to pass the (id)sender by writing:

action:@selector(switchToNewsDetails:)

But I am trying to pass variables like integer values. Writing it this way doesn't work :

int i = 0;
[newsButton addTarget:self
action:@selector(switchToNewsDetails:i)
forControlEvents:UIControlEventTouchUpInside];

Writing it this way does not work either:

int i = 0;
[newsButton addTarget:self
action:@selector(switchToNewsDetails:i:)
forControlEvents:UIControlEventTouchUpInside];

Any help would be appreciated :)

Solution 1:

action:@selector(switchToNewsDetails:)

You do not pass parameters to switchToNewsDetails: method here. You just create a selector to make button able to call it when certain action occurs (touch up in your case). Controls can use 3 types of selectors to respond to actions, all of them have predefined meaning of their parameters:

with no parameters
```
action:@selector(switchToNewsDetails)
```
with 1 parameter indicating the control that sends the message
```
action:@selector(switchToNewsDetails:)
```
With 2 parameters indicating the control that sends the message and the event that triggered the message:
```
action:@selector(switchToNewsDetails:event:)
```

It is not clear what exactly you try to do, but considering you want to assign a specific details index to each button you can do the following:

set a tag property to each button equal to required index

in switchToNewsDetails: method you can obtain that index and open appropriate deatails:

- (void)switchToNewsDetails:(UIButton*)sender{
    [self openDetails:sender.tag];
    // Or place opening logic right here
}

Solution 2:

To pass custom params along with the button click you just need to SUBCLASS UIButton.

(ASR is on, so there's no releases in the code.)

This is myButton.h

#import <UIKit/UIKit.h>

@interface myButton : UIButton {
    id userData;
}

@property (nonatomic, readwrite, retain) id userData;

@end

This is myButton.m

#import "myButton.h"
@implementation myButton
@synthesize userData;
@end

Usage:

myButton *bt = [myButton buttonWithType:UIButtonTypeCustom];
[bt setFrame:CGRectMake(0,0, 100, 100)];
[bt setExclusiveTouch:NO];
[bt setUserData:**(insert user data here)**];

[bt addTarget:self action:@selector(touchUpHandler:) forControlEvents:UIControlEventTouchUpInside];

[view addSubview:bt];

Recieving function:

- (void) touchUpHandler:(myButton *)sender {
    id userData = sender.userData;
}

If you need me to be more specific on any part of the above code — feel free to ask about it in comments.

Solution 3:

Need more than just an (int) via .tag? Use KVC!

You can pass any data you want through the button object itself (by accessing CALayers keyValue dict).

Set your target like this (with the ":")

[myButton addTarget:self action:@selector(buttonTap:) forControlEvents:UIControlEventTouchUpInside];

Add your data(s) to the button itself (well the .layer of the button that is) like this:

NSString *dataIWantToPass = @"this is my data";//can be anything, doesn't have to be NSString
[myButton.layer setValue:dataIWantToPass forKey:@"anyKey"];//you can set as many of these as you'd like too!

Then when the button is tapped you can check it like this:

-(void)buttonTap:(UIButton*)sender{

    NSString *dataThatWasPassed = (NSString *)[sender.layer valueForKey:@"anyKey"];
    NSLog(@"My passed-thru data was: %@", dataThatWasPassed);

}

Solution 4:

Target-Action allows three different forms of action selector:

- (void)action
- (void)action:(id)sender
- (void)action:(id)sender forEvent:(UIEvent *)event

Solution 5:

I made a solution based in part by the information above. I just set the titlelabel.text to the string I want to pass, and set the titlelabel.hidden = YES

Like this :

UIButton *imageclick = [[UIButton buttonWithType:UIButtonTypeCustom] retain];
imageclick.frame = photoframe;
imageclick.titleLabel.text = [NSString stringWithFormat:@"%@.%@", ti.mediaImage, ti.mediaExtension];
imageclick.titleLabel.hidden = YES;

This way, there is no need for a inheritance or category and there is no memory leak