Why cocoa binding won't work with typedef of the framework class

Question

Why there is an error, when trying to bind NSColorWell value to some property...

valueForUndefinedKey: this class is not key value coding-compliant for the key color.

If color property is defined as:

 @property (strong, nonatomic) MyColor *color;

and MyColor is defined as:

typedef NSColor MyColor;

But everything works OK when color property is defined as a NSColor?

Answer 1

You appear to have found a bug, as typedef's should be transparent and not change behaviour.

Testing shows that with:

typedef AnyOldClass SomeOldClass;

and properties in different classes:

@property AnyOldClass *anyclass; // from class A

@property SomeOldClass *someclass; // from class B

then trying to bind the to with bind:toObject:withKeyPath:options: fails. It does appear to work (i.e. non-exhaustive testing) if the typedef is for a value type (e.g. double).

Furthermore it can work if it is changed to:

typedef AnyOldClass *SomeOldClass;

and

@property SomeOldClass someclass; // from class B

that is the typedef is for the pointer type itself. However not the emphasis on can, it doesn't not seem to be consistent between compiles - if it works for a binary it always works for that binary, but a recompilation may break it.

I haven't examined the metadata (at least yet...)

Weird and intriguing. Report it to Apple unless someone jumps in with an explanation soon.

Testing done on Xcode 5.0.2/Clang 4.2