Question

So I’ve been holding off asking this question for a while because I know the solution will most likely be something very very simple. But I have come to the end of my tether so here goes:

I have created a UIButton programatically and linked it to a method, but it is not working!!

.h definition

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface CreaterPage : UIViewController
{
IBOutlet UIView *postcardView;
IBOutlet UIButton *returnButton;
}

-(void)goBack:(UIButton *)button;

@end

.m definition

#import "CreaterPage.h"

@implementation CreaterPage

-(void)viewDidLoad
{
NSLog(@"Creater Page View Loaded Successfully");
UIButton *goHomeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[goHomeButton addTarget:self action:@selector(goBack:) forControlEvents:UIControlEventTouchDown];
[goHomeButton setTitle:@"Go Back" forState:UIControlStateNormal];
goHomeButton.frame = CGRectMake(100, 100, 100, 100);
[self.view addSubview:goHomeButton];
}

-(void)goBack:(UIButton *)button
{
NSLog(@"Home");
}

@end

And basically, when I run the code, the button appears as defined but my program crashes whenever I press it.

In the main.m file, it gives me the error

Thread 1: Program received signal: “EXC_BAD_ACCESS”.

On the line

return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));

I’ve tried all sorts and only turned to creating it programatically because I couldn’t get it working through the interface builder.

So I’m hoping somebody on here can change my juvenile ways and show me where I’m going wrong 😀

Thanks,

Matt

EDIT 1: Changed @selector(goBack) to @selector(goBack:)

Answer 1

My first guess would be that your action is defined as such:

[goHomeButton addTarget:self action:@selector(goBack) forControlEvents:UIControlEventTouchDown];

Note the @selector(goBack) without a colon following the method name. Your method in your .m file is defined as:

-(void)goBack:(UIButton *)button

So I imagine changing your action to @selector(goBack:) would clear things up.

Sidenote: It’s very uncommon to define the type of the sender for an IBAction, as you have done. While you might not encounter any issues as long as your UIButton is the only UI object that causes the method to be called, it’s very poor practice. You should change your method signature to:

-(IBAction)goBack:(id)sender

Note also the use of IBAction in place of void. While they’re syntatically the same thing, the IBAction makes it clear to readers, and to Interface Builder, which methods are available for linking.