CODEWITHSUNDEEP
iosobjective-ciphonekey-value-observing
user
user

Reputation: 85

KVO not working (observing another class's property)

I'm trying to observe a property variable (xxx) of ResultDataClass. In my working ViewController, I wrote the following.

-(void)dealloc {    
    ResultDataClass *resultData = [ResultDataClass getInstance];
    [resultData addObserver:self forKeyPath:@"xxx" options:NSKeyValueObservingOptionNew context:NULL];
}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    self.solutionText.text = @"test1";

    if([keyPath isEqualToString:@"xxx"]) {
        self.solutionText.text = @"test2";
    }

}

solutionText is a UITextView in my working ViewController. After running the program, nothing was shown in the textview.

Anyone know how to fix this?

Thank you and sorry for my English.

Upvotes: 1

Views: 1030

Answers (1)

Midhun MP
Midhun MP

Reputation: 107231

You written the observer in dealloc method. There will be an issue, your object is being released when you are adding an observer, so there will be a crash when the KVO value is changed.

There is no crash and nothing is working, I think the reason is; the dealloc method is never called. It means your view controller is never released (potentially a leak, a strong retain cycle is there).

Instead of that add that in your viewDidLoad:

- (void)viewDidLoad
{    
    [super viewDidLoad];
    ResultDataClass *resultData = [ResultDataClass getInstance];
    [resultData addObserver:self forKeyPath:@"xxx" options:NSKeyValueObservingOptionNew context:NULL];
}

Upvotes: 1

Related Questions