UIButton target action inside custom class - ios

Question

I've been struggling with a bug, and I found a work-around, but I'd like to understand what is exactly going on. it has something to do with UIButton target actions misfiring depending on different subview hierarchies, inside a subclass.
Brief summary: I have a subclass of NSObject with a UIView property object, a UIButton attached to it, and a target added to the button calling a function inside the subclass. Inside the main ViewController, I init the subclass and add its view to the view stack, click the button, and it throws me to main.mm with the error - EXC_BAD_ACCESS, gives me little feedback. so the hierarchy looks like this:
-CustomClass
--UIView <-this is added as a subview to the View Controller
---UIButton (onRelease calling a function)
so I fixed it by changing the custom class to be a subclass of UIView instead of NSObject, then add its #property UIView to be a subview of the custom class (and the button is still attached to the subview), and then in the main View Controller, I add the custom class itself as a subview, not the class's subview property object. then the button successfully calls the function. so the new arrangement looks like this:
-CustomClass (now UIView) <-this is added as a subview to the View Controller
--UIView <-this is added as a subview to CustomClass
---UIButton (onRelease calling a function)
then, i realized i can just keep the CustomClass a subclass of UIView for both instances, the problem persists with the original setup if everything else is unchanged.
okay, more detail, here's code:
CustomClass:
.h
#interface Temp : UIView
#property UIView *subview;
#property UIButton *but;
#end
.m
-(id) init{
self = [super initWithFrame:[[UIScreen mainScreen] bounds]];
if(self){
_subview = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
//[self addSubview:_subview]; // FOR THE FIX
_but = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[_but setTitle:#"OKAY" forState:UIControlStateNormal];
[_but setBackgroundColor:[UIColor blackColor]];
[_but setFrame:CGRectMake(50, 50, 200, 200)];
[_subview addSubview:_but];
[_but addTarget:self action:#selector(pageTurn) forControlEvents:UIControlEventTouchUpInside];
}
return self;
}
-(void) pageTurn{
NSLog(#"WORKS");
}
inside view controller:
Temp *temp = [[Temp alloc] init];
[self.view addSubview:temp.subview];
//[self.view addSubview:temp]; // FOR THE FIX, instead of above line

Answer 1

Who's holding onto temp?
If temp isn't referenced by anyone then it's released. At that point the target is zombie and of course you will crash. temp.subview is being held by self.view.
In the second setup, adding temp as a subview of self.view keeps a reference to it.
You can fix this by adding a Temp * property in the view controller.
self.temp = [[Temp alloc] init];
[self.view addSubview:self.temp.subview];

Answer 2

You're messing with all kinds of view hierarchy stuff you don't need to, which is likely the cause of the problem. I created a Test UIView subclass that had a UIButton instance variable that I added as a subview in the Test object, there's no need to add another view as a subview and then add the button to the subview, and then in your view controller add the button's subview to the view - it's WAY more complicated than it needs to be.
In a nutshell - Create the Temp UIView, add the button as a subview, then in your view controller class add the Temp UIView as a subview. Simple as that, here is the code:
- (id)init {
self = [super initWithFrame:[[UIScreen mainScreen] bounds]];
if(self){
_but = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[_but setTitle:#"OKAY" forState:UIControlStateNormal];
[_but setBackgroundColor:[UIColor blackColor]];
[_but setFrame:CGRectMake(100, 100, 200, 200)];
[_but addTarget:self action:#selector(pageTurn) forControlEvents:UIControlEventTouchUpInside];
[self addSubview:_but];
}
return self;
}
- (void)pageTurn {
NSLog(#"WORKS");
}
Then added an instance to my view controller:
Test *temp = [[Test alloc] init];
temp.backgroundColor = [UIColor redColor];
[self.view addSubview:temp];
This was the result: