iPhone - nil button outside the method?

I am creating a button like this inside a method:

UIButton * btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
btn.frame = CGRectMake(0, 0, 100, 50);
[btn setTitle:@"Hello, world!" forState:UIControlStateNormal];
[self.view addSubview:btn];

myButton = btn; 
// I am saving the btn reference to this ivar declared on .h as UIButton.

At another point of the code I try to use myButton and it is always nil.

I have tried to retain btn after assigning it to myButton on the original method but myButton is always nil.

self.view is always there. btn is never re开发者_如何学JAVAleased.

Why myButton is nil?

I know I can create the button using alloc, but I am just trying to understand this.

thanks.

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UIButton * btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

here you get an autorelease object of UIButton.

if want to access this button at other places so for this purpose,make it a property and use

UIButton * btn = [[UIButton buttonWithType:UIButtonTypeRoundedRect] retain];

or creating by alloc and release it in dealloc .

Edit

in .h

@property (nonatomic,retain) UIButton *myButton;

and in .m

self.myButton=btn;

and release it in dealloc.

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OK. You should try the below code

UIButton * btn = [[UIButton buttonWithType:UIButtonTypeRoundedRect] retain];

myButton = btn;

It will surely work.

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At another point of the code, my guess is that you are using a different MyButton variable than the one you assigned from btn. Perhaps an instance inside a different object, or a local covering the instance, etc.

The btn object should be retained by the addSubView call. But if you remove this button from being a subview, it will be autoreleased.

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Because nowhere u have initialized the Button, that is why its giving u nil value.