Question

I regularly use lazy loading to instantiate custom classes, arrays, etc. The pattern is typically:

@property (strong, nonatomic) Class *class;

...

- (Class *)class
{
    if(!_class) _class = [[Class alloc]init];
    return _class;
}

Is it possible to use the same pattern to configure UI elements? For example, instead of formatting all my buttons and views in ViewWillAppear, I would like to put the formatting in the getter. For example:

- (UIButton *)button
{
    if(!_button) {
        _button = [[UIButton alloc]init];
        self.button.backgroundColor = [UIColor redColor];
    }
    return _button;
}

The problem is I am using a storyboard and XCode instantiates the button so asking if it is nill should always return false. So the background will never be changed. If I remove the if-then, then the background will be set every time the getter is accessed which is probably OK but not optimal.

So, how do I use a UI element’s getter to configure the element?

Answer 1

If this is really the way you want to do it, just use a BOOL flag. For example:

@interface MyClass() {

    BOOL _hasCustomisedButton;
}

@property (strong, nonatomic) UIButton *button;

@end

@implementation MyClass


- (UIButton *)button {

    if (_hasCustomisedButton || _button == nil) {
        // check for nil button as well in case the nib isn't loaded yet
        return _button;
    }

    [_button setBackgroundColor:[UIColor redColor]];

    _hasCustomisedButton = YES;

    return _button;
}

@end