Question

My iPhone app is quite simple, however it errors out. My app delegate opens up this view controller:

#import "Launch.h"

@implementation Launch

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad {
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor redColor];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    button.frame = CGRectMake(100, 100, 100, 100);
    [button setTitle:@"Hello" forState:UIControlStateNormal];
    [button addTarget:self action:@selector(buttonPressed) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button];
}

-(void)buttonPressed {
    NSLog(@"Button Pressed!");
}

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo {
    //image.image = img;
    [[picker parentViewController] dismissModalViewControllerAnimated:YES];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

which is just a red screen with a button. When I click the button, the app errors out with no error message. Why?

here is my main.m method, and when the program errors out, it points to the “return” line and indicates an EXEC_BAD_ACCESS in a thread.

#import <UIKit/UIKit.h>

#import "testAppDelegate.h"

int main(int argc, char *argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([testAppDelegate class]));
    }
}

Answer 1

The target class has been deallocated, it needs to be retained.

From the Apple docs:

addTarget:action:forControlEvents:

When you call this method, target is not retained.

You need to insure the class instance is retained.