Objective-C categories: Can I add a property for a method not in my category?
Here's the warning you're getting:
warning: property ‘foo’ requires method '-foo' to be defined - use @synthesize, @dynamic or provide a method implementation
To suppress this warning, have this in your implementation:
@dynamic foo;
If something's declared in your category's interface, its definition belongs in your category's implementation.
I wrote two articles on this, though the concept is slightly different from the question you're asking.
- Add properties to categories without touching the base class: http://compileyouidontevenknowyou.blogspot.com/2012/06/adding-properties-to-class-you-dont.html
- Access iVars from categories: http://compileyouidontevenknowyou.blogspot.com/2012/06/if-you-want-to-keep-everything-in-your.html
This is a LOT better than method swizzling, at least: way safer.