Re-Casting a Property in Subclasses

Question

I have a set up where I have a hierarchy of view types with an equivalent hierarchy of model types. The set up is as follows:

The node model / data:

@interface GenericNode : NSObject
//blah blah blah
@end
@interface ShapeNode : GenericNode
//more blah
@end

the nodeViews, which will always receive an equivalently typed node as its model:

@interface GenericNodeView : UIView
@property (nonatomic, strong) GenericNode * model;
@end
@interface ShapeNodeView : GenericNodeView
@end

However, the problem here is that the type of the model is always retained as the abstract superclass, forcing me to cast it every single time I want to access methods of properties of the subclasses.

Is there a way to recast class properties such that exampleShapeNodeView.model always returns an instance of ShapeNode and so on?

I have tried custom accessor methods such as

@interface GenericNodeView : UIView
@property (nonatomic, strong) GenericNode * model;
-(GenericNode *)myModel;
@end
@interface ShapeNodeView : GenericNodeView
-(ShapeNode *)myModel;
@end

//in genericNodeView implementation
-(GenericNode *)myModel{
  return (GenericNode *) self.model;
}

//in shapeNodeView implementation
-(ShapeNode *)myModel{
  return (ShapeNode *) self.model;
}

but calling [exampleShapeNodeView myModel] still returns a GenericNode;

Answer 1

I just tested this out, and it worked great for me:

In the child class, redeclare with the @property:

@interface GenericNodeView : UIView
@property (nonatomic, strong) GenericNode * model;
@end
@interface ShapeNodeView : GenericNodeView
@property (nonatomic, strong) ShapeNode * model;
@end

You need to re-@synthesize as well, but there were no complaints by my Xcode (4.3.3)