Is it necessary to override bind:toObject:withKeyPath:options: in an NSView subclass to implement binding?

Question

I have an NSView subclass which has property which I want to be bindable. I\'ve implemented the following in the subclass:

myView.h:

@property (readwri         


        

Answer 1

No, you shouldn’t need that glue code.

What do you mean by “doesn’t seem to be the case”? What happens if you omit it?

Answer 2

No, it is not necessary to override bind:.

As Peter Hosey wrote in the comment to the earlier answer, you can call exposeBinding: and implement KVC- and KVO-compliant accessors and setters.

MyView.h:

@interface MyView : NSView {
    NSArray *_representedObjects;
}

// IBOutlet is not required for bindings, but by adding it you can ALSO use
// an outlet
@property (readonly, retain) IBOutlet NSArray *representedObjects;

@end

MyView.m:

+ (void)initialize {
    [self exposeBinding:@"representedObjects"];
}

// Use a custom setter, because presumably, the view needs to re-draw
- (void)setRepresentedObjects:(NSArray *)representedObjects {
    [self willChangeValueForKey:@"representedObjects"];
    // Based on automatic garbage collection
    _representedObjects = representedObjects;
    [self didChangeValueForKey:@"representedObjects"];

    [self setNeedsDisplayInRect:[self visibleRect]];
}

Then you can set the binding programmatically:

[myView bind:@"representedObjects" toObject:arrayController withKeyPath:@"arrangedObjects" options: nil];

To set the binding in Interface Builder, however, you must create a custom palette.

Answer 3

You definitely DO need to implement -bind:toObject:withKeyPath:options: in a custom view if you want to implement bindings in that view. Your implementation in myView.m is pretty much spot on.