Objective-C: Passing a selector to an object

Question

Hey,

I'm implementing a button class in cocos2d, and I want to be able to pass the selector when the button is created. Here is Button.m:

#import "CCButton.h"


@implementation CCButton

+(CCButton*) buttonFromImage:(NSString*)image selectedImage:(NSString*)selectedImage atPosition:(CGPoint)position  selector:(SEL)selector_method
{
    CCMenuItem *menuitem = [CCMenuItemImage itemFromNormalImage:image selectedImage:selectedImage target:self selector:selector_method];

    menuitem.position = position;
    CCButton *menu = [CCMenu menuWithItems:menuitem, nil];
    menu.position = CGPointZero;
    return menu;
}

@end

It inherits from CCMenu. What I want to do is define the selector method wherever create my button. For example, if I have a menu, I want the selector to be in the menu, and assign the selector to the button (in menu.m):

backButton = [CCButton buttonFromImage:@"image1.png" selectedImage:@"image2.png" atPosition:ccp(120,70) selector:@selector(backTouched:)];
        [self addChild:backButton z:1];

...

- (void)backTouched:(id)sender {
    //do what i want the button to do here
}

This crashes when I touch the button. How do I implement what I want?

Thanks for the help, Dave

Edit: the error I get is bad pointer, SIGABRT

Answer 1

The target cannot be self. The target has to be the class that implements the button you have created.

When passing in the selector as you create the button, also pass in the target of the button creating class.

In other words, target is the class that contains the method that you pass as the selector.

Hope that made things clear :)

PS: Here's what you should try. Note that your buttonFromImage now takes in a target attribute which is set when you create the backbutton. Also the target that you set in your buttonFromImage is not self, but the target that comes in from the buttonFromImage method.

@implementation CCButton

+(CCButton*) buttonFromImage:(NSString*)image selectedImage:(NSString*)selectedImage atPosition:(CGPoint)position selector:(SEL)selector_method target: (id)target { CCMenuItem *menuitem = [CCMenuItemImage itemFromNormalImage:image selectedImage:selectedImage target:target selector:selector_method];

    menuitem.position = position;
    CCButton *menu = [CCMenu menuWithItems:menuitem, nil];
    menu.position = CGPointZero;
    return menu;

}

@end

//***************************

backButton = [CCButton buttonFromImage:@"image1.png" selectedImage:@"image2.png" atPosition:ccp(120,70) selector:@selector(backTouched:) target:self]; [self addChild:backButton z:1];

//...

• (void)backTouched:(id)sender { //do what i want the button to do here }

Answer 2

There are a couple of things that could be the problem, but none of them have anything to do with passing a selector:

1. You're passing self (which in a class method is the CCButton class) as the target of the button, but CCButton does not have a corresponding class method, and it's almost certainly not the object that you intend to respond to the action.

2. Your method says it returns a CCButton, but you're actually returning a CCMenu. Unless CCButton and CCMenu are structurally identical (i.e. CCButton has no instance variables), this is almost guaranteed to cause a crash, and is wrong in any case.