Passing parameters to addTarget:action:forControlEvents

user_477274 0
Viewed 121397

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 :)

uicontrolevents objective-c iphone cocoa-touch ios
13 Answers

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!

*Note: The key shouldn't be a default key of a CALayer property, consider adding a unique prefix to all of your keys to avoid any issues arising from key collision.

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);

}
user_20571710

This fixed my problem but it crashed unless I changed 

action:@selector(switchToNewsDetails:event:)

to

action:@selector(switchToNewsDetails: forEvent:)
user_4909660

If you just want to change the text for the leftBarButtonItem shown by the navigation controller together with the new view, you may change the title of the current view just before calling pushViewController to the wanted text and restore it in the viewHasDisappered callback for future showings of the current view.

This approach keeps the functionality (popViewController) and the appearance of the shown arrow intact.

It works for us at least with iOS 12, built with Xcode 10.1 ...

user_107777890
Related