Category +load timing issue

Question

I have a class hierarchy as follows

@interface PTLDatasource : NSObject
...
@interface PTLFetchedDatasource : PTLDatasource
...

And I want to add platform specific extensions to these classes that are defined in a protocol and implemented in a category:

@protocol PTLTableViewDatasource
- (void)foo;
...
@interface PTLDatasource (TableViewExtensions) <PTLTableViewDatasource>
...
@interface PTLFetchedDatasource (TableViewExtensions) <PTLTableViewDatasource>
...

A basic implementation of -foo: is done in the PTLDatasource category. However, I also need a custom implementation of -foo: in PTLFetchedDatasource which may then fallback to the PTLDatasource implementation.

Currently I'm trying to swizzle the implementations in PTLFetchedDatasource (TableViewExtensions) in +load, but I'm running into issues where +load in PTLFetchedDatasource (TableViewExtensions) is called before +load in PTLDatasource (TableViewExtensions), so swizzling fails because the PTLDatasource implementation of -foo: doesn't exist yet.

Is there a way to work around this load timing issue?

Do I even need swizzling? I know that overriding class member methods in a category is a no-no, but could I just call [super foo:] from the PTLFetchedDatasource (TableViewExtensions) implementation?

Thanks.

Answer 1

Mike Ash confirmed for me that swizzling is unnecessary and I can just call through to super. The only concern with overriding the category method would be if it was done multiple times on the same class.