Problem Subclassing CALayer

[AdColvin]

I want to create some layers that have some custom properties.

So I created a class that subclassed from CALayer and I added these new properties there.

But in some cases, I had trouble accessing the properties of CALayer through this class.

I created the layers in a view class, which worked fine:

layer = [CustomLayer layer];
layer.frame = CGRectMake (0, 0, 58, 88);
layer.position = CGPointMake (250, 160);
layer.backgroundColor = [[UIColor redColor] CGColor];

But then, when I try to manipulate the view from the view controller, I get an error. For instance:

myView.layer.position = CGPointMake (20, 160);

When I use CALayer, this code works fine. But now that I'm inheriting from it, it produces an error saying that the property has not been found for this class.

Does anyone know why I'm not being allowed to do this?

Any help appreciated,
Thanks,
Adam

[Duncan C]

Originally Posted by AdColvin

I want to create some layers that have some custom properties.

So I created a class that subclassed from CALayer and I added these new properties there.

But in some cases, I had trouble accessing the properties of CALayer through this class.

I created the layers in a view class, which worked fine:

layer = [CustomLayer layer];
layer.frame = CGRectMake (0, 0, 58, 88);
layer.position = CGPointMake (250, 160);
layer.backgroundColor = [[UIColor redColor] CGColor];

But then, when I try to manipulate the view from the view controller, I get an error. For instance:

myView.layer.position = CGPointMake (20, 160);

When I use CALayer, this code works fine. But now that I'm inheriting from it, it produces an error saying that the property has not been found for this class.

Does anyone know why I'm not being allowed to do this?

Any help appreciated,
Thanks,
Adam

Show us the header file for your custom CALayer subclass CustomLayer

[AdColvin]

Originally Posted by Duncan C

Show us the header file for your custom CALayer subclass CustomLayer

Of course, here it is:

@class CALayer;

@interface CustomLayer : CALayer 
{
    CFTimeInterval time;
    CGPoint startPoint;
    CGPoint endPoint;
}

@property CFTimeInterval time;
@property CGPoint startPoint;
@property CGPoint endPoint;

@end

When a layer is animating from one point to another, I need a way of figuring out its exact position on screen at any one time. These properties were to help me do that.
Thanks,
Adam

[Duncan C]

Originally Posted by AdColvin

Of course, here it is:

@class CALayer;

@interface CustomLayer : CALayer 
{
    CFTimeInterval time;
    CGPoint startPoint;
    CGPoint endPoint;
}

@property CFTimeInterval time;
@property CGPoint startPoint;
@property CGPoint endPoint;

@end

When a layer is animating from one point to another, I need a way of figuring out its exact position on screen at any one time. These properties were to help me do that.
Thanks,
Adam

position is probably a "fake" property that has a setter, but not an iVar. I've run into odd compiler issues with properties before where the "dot notation" won't work, but the setter form will. Try rewriting your line like this:


[myView.layer setPosition: CGPointMake(x,y)];

Also, if you want to change one of the properties of your custom subclass of CALayer, remember you need to cast the view property to your custom type before you can refer to your custom properties:

CustomLayer* myViewCustomLayer = (CustomLayer*)myView.layer;
myViewCustomLayer.time = [NSDate timeIntervalSinceReferenceDate];

[AdColvin]

Thanks for the help, I thought that had solved it. Only now, when I want to retrieve the position of the layer, by writing this:

[myView.layer position];

I get a warning telling me that there are multiple methods named "position". It doesn't do this when try to set the position.

I haven't written any methods called position myself. Any ideas why this might be happening?

Again, thanks a lot for the help.

[Duncan C]

Originally Posted by AdColvin

Thanks for the help, I thought that had solved it. Only now, when I want to retrieve the position of the layer, by writing this:

[myView.layer position];

I get a warning telling me that there are multiple methods named "position". It doesn't do this when try to set the position.

I haven't written any methods called position myself. Any ideas why this might be happening?

Again, thanks a lot for the help.

No, I don't know why you're getting that warning. Odd.

BTW, you should almost always declare your properties as (nonatomic).

If you don't, the system adds code that applies multi-threading locks to your getters and setters, which slows down your code unnecessarily. The only time you want your properties to be atomic is if you're reading/writing them from multiple threads at the same time.