Question

I am basically trying to add two view controllers to one controller.

I created a view based application called “MultipleViews”. After that i add two controller classes “RedView.h” and “BlueView.h” with their own xibs. I am able to add the views of both the controllers to “MutipleViewsViewController” by the method [self.view addSubview:red.view]. Both the views are displayed properly. The problem is when I add a button to the red and blue controllers. Whenever I click the button it says unrecognized selector sent to instance even though I linked the buttons with their functions properly. Am i missing something here?

here is the code:

MultipleViewsViewController.h

#import <UIKit/UIKit.h>

@interface MutipleViewsViewController : UIViewController {

}

@end

MutipleViewsViewController.m

–

 (void)viewDidLoad {
    [super viewDidLoad];

    RedView *red = [[RedView alloc]init];

    red.view.frame = CGRectMake(0, 0, 320, 240);

    [self.view addSubview:red.view];

    BlueView *blue = [[BlueView alloc]init];

    blue.view.frame = CGRectMake(0, 240, 320, 240);

    [self.view addSubview:blue.view];



}

RedView.h

#import <UIKit/UIKit.h>


@interface RedView : UIViewController {

}

-(IBAction)buttonPressed;

@end

BlueView.h

#import <UIKit/UIKit.h>


@interface BlueView : UIViewController {

}

-(IBAction)buttonPressed;

@end

The buttons are linked to the buttonPressed method through IB.
The message i get when i click the button in the red view is:

MutipleViews[1865:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[RedView buttonPressed]: unrecognized selector sent to instance 0x4e12500'

Sorry for not being clear earlier.

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Answer 1

The IBActions typically take an input parameter of type id. So your buttonPressed action should look like

-(IBAction)buttonPressed:(id)sender;

When this action is actually called, a reference to the control which calls it (in this case the button) is passed.

When calling it programatically, you can send the controller’s object (self) to it.