how to call @selector method from another class

user3266009 picture user3266009 · Feb 13, 2014 · Viewed 10.1k times · Source

is it possible to call @selector methods from another class ? for example i make a method "bannerTapped:" and call it from "myViewController.m" class.

myviewcontroller.m :

anotherClass *ac= [[anotherClass alloc]init];

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc]initWithTarget:ac action:@selector(bannerTapped:)];
singleTap.numberOfTapsRequired = 1;
singleTap.numberOfTouchesRequired = 1;
cell.conversationImageView.tag = indexPath.row;
[cell.conversationImageView addGestureRecognizer:singleTap];
[cell.conversationImageView setUserInteractionEnabled:YES];

anotherClass.m :

-(void)bannerTapped:(UIGestureRecognizer *)gestureRecognizer {
    //do something here 
}

updated :

viewController.m:

 #import "anotherClass.h"



 +(viewcontroller *)myMethod{
 // some code...

 anotherClass *ac= [[anotherClass alloc]init];

    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc]initWithTarget:ac   action:@selector(bannerTapped:)];

}

anotherClass.h:

-(void)bannerTapped:(UIGestureRecognizer *)gestureRecognizer;

anotherClass.m:

-(void)Viewdidload{
    [viewController myMethod];
     }


   -(void)bannerTapped:(UIGestureRecognizer *)gestureRecognizer {
      //do something here 
   }

Answer

Simon McLoughlin picture Simon McLoughlin · Feb 13, 2014

Yes, like this

initWithTarget:anotherClassInstance action:@selector(bannerTapped:)];

The Target is the class instance you want to send the event to.

EDIT

Please learn to post all of your code in future as you question is FAR more complex than you have asked. Long story short you can't do this:

+(viewcontroller *)myMethod{

   anotherClass *ac= [[anotherClass alloc]init];

   UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc]initWithTarget:ac   action:@selector(bannerTapped:)];

}

As soon as this method finishes, ac will be released form memory as the scope it was created in is now gone. Using ARC makes no difference here.

You need to understand some different things here:

  • +(void) makes this a class method, meaning you can't create an instance variable of ac which is what you are trying to do in some sense, but you are still creating it in the wrong place.
  • I would suspect (just guessing based on the code) that you think ac is pointing to a viewController that is currently in the navigation stack. ac is a brand new copy of that class. You have created a new copy that is not displayed anywhere or used anywhere and dies as soon as that method has finished.

My first piece of code answers the question you asked, that is how you call a selector from another class. Your issue now is that you don't understand the flow of objects, memory management, class instances and class methods vs instance methods.

Please study objective-c and object oriented programming more and try this again.