检测UILabel文本中的更改

Question

是否可以为UILabel的文本属性更改时设置通知？当我找不到UILabel时,我尝试了用于UITextFields的那个,但它没有用.

 [[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(posttosocial)
 name:UITextFieldTextDidChangeNotification
 object:nowplaying];

Answer 1

您可以使用键值观察(KVO):

[label addObserver:self
        forKeyPath:@"text"
           options:NSKeyValueObservingOptionNew
                 | NSKeyValueObservingOptionOld
           context:NULL];

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"text"]) {
        /* etc. */
    }
}