问题
For the life of me I can't get KVO working with UISwitch. I have a custom UITableViewCell with a UISwitch added through Interface Builder. I created an IBOutlet for the UISwitch and linked it to theSwitch
variable.
- (id)initWithCoder:(NSCoder *)coder {
self = [super initWithCoder:coder];
if (self) {
[theSwitch addObserver:self forKeyPath:@"on" options:NSKeyValueObservingOptionNew context:NULL];
}
return self;
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
NSLog(@"toggled switch");
}
observeValueForKeyPath:ofObject:change:context is never called!
回答1:
I'm not sure, but it's possible that UISwitch simply isn't KVO-compliant.
No matter, because you can just use control events:
[theSwitch addTarget:self action:@selector(switchChanged:) forControlEvents:UIControlEventValueChanged];
// ...
- (void)switchChanged:(UISwitch *)sender {
if (sender.on) {
// ...
}
}
回答2:
theSwitch might not have been initialized when you add the observer. try adding the observer in awakeFromNib.
来源:https://stackoverflow.com/questions/7193958/kvo-not-working-with-uiswitch