问题
I'm trying to build a static class called Logger that will upload the log files at some point, when called like [Logger uploadLogFiles].
I'm trying to add an observer to this static class like so:
[Logger addObserver:self forKeyPath:@"uploadComplete" options:NSKeyValueObservingOptionNew context:nil];
I do this just before starting an asynchronous call method for NSURLConnection. I do get a warning, saying Incompatible pointer types sending Class to parameter of type NSObject *.
However, this does not seem to work, as the observerValueForKeyPath: method never gets called.
Has anybody had any experience with adding observers to static variables in static classes?
Thanks!
回答1:
A Class has no instance variables, so there is nothing to observe.
You need to have an actual object (an instance of a class) for KVO.
来源：https://stackoverflow.com/questions/9078595/how-does-addobserverforkeypath-work-on-a-static-class