这是我的代码:
__block UIButton buttonOne;
__block UIButton buttonTwo;
- (UIView *)addressOptionView
{
if (!_addressOptionView) {
_addressOptionView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.view.frame), addressButtonArray.count * BasedAdditionForSegment)];
void (^setupButton)(UIButton *, NSString *, NSInteger) = ^
void (UIButton *button, NSString *title, NSInteger idx) {
if (!button)
button = [[UIButton alloc] init];
button.frame = ({
CGRect frame = _addressOptionView.bounds;
frame.origin.x += 20;
frame.size.width -= 40;
frame.origin.y = idx * BasedAdditionForSegment;
frame.size.height = BasedAdditionForSegment;
frame;
});
[button setTitle:title forState:UIControlStateNormal];
};
setupButton(buttonOne, addressButtonArray[0], 0);
setupButton(buttonTwo, addressButtonArray[1], 1);
DebugLog(@"%@", buttonOne);
[_addressOptionView addSubview:buttonOne];
[_addressOptionView addSubview:buttonTwo];
}
return _addressOptionView;
}
buttonOne
和buttonTwo
不是属性。调用
addressOptionView getter
之后,这两个按钮会立即释放,因此它们不会显示在视图中(我想在NSLog
时为nil)。我将
setupButton
块更改为@property
,它也不起作用。将两个按钮更改为
@property
也不起作用。但是,当我将
setupButton
块更改为UIButton * (^setupButton)(NSString *, NSInteger)
确实出现了两个按钮,但是以后我无法以其他方法(已经
nil
)访问它们。有人可以简要说明我做错了什么吗?我该如何运作?
谢谢。
最佳答案
@implementation SomeObject {
// do not make these __block types
UIButton* _buttonOne;
UIButton* _buttonTwo;
}
- (UIView *)addressOptionView
{
// most of method removed for brevity, see question
void (^setupButton)(UIButton*__autoreleasing*, NSString *, NSInteger) = ^
void (UIButton*__autoreleasing*button, NSString *title, NSInteger idx) {
NSAssert( button, @"Must not pass nil reference as button" );
UIButton* localButton = *button;
if (!localButton) {
// continue to work on the more convenient localButton, but make sure
// that the button reference is written to the ivar...
localButton = *button = [UIButton buttonWithType:UIButtonTypeCustom];
}
// other button setup clipped
};
// compiler will generate strong stack-allocated temporary variable here
// to deal with autoreleasing assignment, but make sure ivars are not
// __block class
setupButton(&_buttonOne, addressButtonArray[0], 0);
setupButton(&_buttonTwo, addressButtonArray[1], 1);
DebugLog(@"%@", _buttonOne);
[_addressOptionView addSubview:_buttonOne];
[_addressOptionView addSubview:_buttonTwo];
// top-most branch was clipped for this example
return _addressOptionView;
}
关于ios - 初始化内部块后对象变为零,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/24644844/