Passing selector to a custom method to create UIButton programmatically

Question

I am using XCode 5 under ios 7 to do a simple project. And I get the following error when I press a button that is created programmatically:

2013-11-10 09:16:02.969 Project2[446:70b] +[KNSunDynamicUIButton buttonSavePressed:]: unrecognized selector sent to class 0x221424

Details:
I create a custom method that is used to create a UIButton object programmatically. That custom method is used in any view controller. That custom method needs passed-in parameters like x, y, width, height, button title, and selector that is an event handler and passed in like "(SEL)selector".

Custom method (belongs to a helper class):

+(UIButton*)kNSunSetupWithSelector:(SEL)selector    withX:(int)x y:(int)y width:(int)width height:(int)height
                       buttonTitle:(NSString*)buttonTitle backGroundColor:(CGColorRef) backGroundColor
{

    UIButton* button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

    [button setTitle:@"Save" forState:UIControlStateNormal];
    button.frame = CGRectMake(x, y, width, height);
    button.backgroundColor = [UIColor greenColor];

// selector is used over here
    [button addTarget:self
                    action:selector
          forControlEvents:UIControlEventTouchDown];

    return button;
}

And then in a view controller .m file, I call that custom method like:

-(void)setUpButtons
{
            SEL selector = @selector(buttonSavePressed:);
            _buttonSave = [KNSunDynamicUIButton kNSunSetupWithSelector:selector withX:470 y:410 width:160 height:40 buttonTitle:@"Save" backGroundColor:(_buttonSaveColor)];

            [self.view addSubview:_buttonSave];

}

    @interface MyViewController ()
    {
    ...

        // buttons
        UIButton* _buttonSave;
    }
    @end

And the definition of button's event handler in the same view controller .m file like:

- (void)buttonSavePressed:(UIButton*)button
{
    NSLog(@"Button Save clicked.");
}

When I run my code and hit over the button, I see the exception as mentioned above. Please help thank you.

P.S. If I rewrite the custom method as an alternative that does not have "(SEL)selector" parameter in its signature, and let controller view, who calls that custom method, does the job of coding selector, then there is no exception:

-(void)setUpButtons
{
    //Note: the codes are in my view controller .m file

_buttonSave = [KNSunDynamicUIButton kNSunSetupWithX:470 y:410 width:160 height:40 buttonTitle:@"Save" backGroundColor:_buttonSaveColor];


   // Note: selector coding is taken care by codes of my view controller instead of by custom method
   [_buttonSave addTarget:self
    action:@selector(buttonSavePressed:)
    forControlEvents:UIControlEventTouchDown];



    [self.view addSubview:_buttonSave];
    [_buttonSave setupView];
}

And the alternative custom method (I do not like the method because it does not take care of dynamic passed-in selector):

+(UIButton*)kNSunSetupWithX:(int)x y:(int)y width:(int)width height:(int)height
                   buttonTitle:(NSString*)buttonTitle backGroundColor:(CGColorRef) backGroundColor
{
    UIButton* button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

    [button setTitle:@"Save" forState:UIControlStateNormal];
    button.frame = CGRectMake(x, y, width, height);
    button.backgroundColor = [UIColor greenColor];

    return button;
}

Igor Igor · Accepted Answer · 2013-11-10T16:45:24

The problem is line in helper class:

[button addTarget:self action:selector forControlEvents:UIControlEventTouchDown];

Here you said that the helper class will have method you're passing through selector, in you're case buttonSavePressed: method.

You should add inController parameter in you're helper method to tell in which controller is selector method placed.

In your particular case, the helper method should looks something like this (Note that inController parameter is added right after selector parameter):

+(UIButton*)kNSunSetupWithSelector:(SEL)selector
                      inController:(UIViewController*)controller
                             withX:(int)x
                                 y:(int)y
                             width:(int)width
                            height:(int)height
                       buttonTitle:(NSString*)buttonTitle
                   backGroundColor:(CGColorRef) backGroundColor
{

UIButton* button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

[button setTitle:@"Save" forState:UIControlStateNormal];
button.frame = CGRectMake(x, y, width, height);
button.backgroundColor = [UIColor greenColor];

// selector is used over here
[button addTarget:controller
           action:selector
 forControlEvents:UIControlEventTouchDown];

    return button;
}

and you should call it, from your controller this way:

-(void) setupButtons
{
    SEL selector = @selector(buttonSavePressed:);
    _buttonSaveColor = [UIColor orangeColor].CGColor;
    _buttonSave = [KNSunDynamicUIButton kNSunSetupWithSelector:selector
                                                  inController:self
                                                         withX:470
                                                             y:410
                                                         width:160
                                                        height:40
                                                   buttonTitle:@"Save"
                                               backGroundColor:(_buttonSaveColor)];

    [self.view addSubview:_buttonSave];
}

Passing selector to a custom method to create UIButton programmatically

1 Answers