Question

My previous question asked for a way to keep a text view and slider in sync with bindings when modifying a CGRect’s “x” value.

Following Peter Hosey’s advice on using the controller’s setter to propogate those changes to the CALayer, I came up with the following:

@interface WindowController : NSObject {
  CALayer *layer;
  float frameOriginX;
}
@end

@implementation WindowController
...
-(void)setFrameOriginX:(id)value {
  [layer setValue:[NSNumber numberWithFloat:[value floatValue]] 
       forKeyPath:@"frame.origin.x"];
  frameOriginX = [value floatValue];

}

-(float)frameOriginX {
 return [[layer valueForKeyPath:@"frame.origin.x"]floatValue];
}
@end

I used bindings to connect the text view and slider to “self.frameOriginX” and it’s all working–both controls update each other. However, I was wondering what a cleaner way to do this is.

Thank You,

Charles

Answer 1

First off, why does setFrameOriginX: take an id and frameOriginX return a float? KVC will not like this. Plus, you should use CGFloat, not float.

Once you fix that, you’re in luck. Today, Colin Barrett released SSGeometryKVC. With that, your setter becomes:

-(void)setFrameOriginX:(CGFloat)newX {
    frameOriginX = newX;
    [[layer mutableRectValueForKey:@"frame"].x = frameOriginX;
}

Note that neither this implementation nor your original implementation is thread-safe. This won’t be a problem as long as it’s only the controls that are calling it.

I used bindings to connect the text view and slider to “self.frameOriginX”…

Huh? If you bound them to the controller, you don’t need self. here.