Support Root Classes #4
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added 5 commits
September 28, 2010 22:26
These changes started out as something simple: get an NSArray with the root classes. Unfortunately, collections, including NSArray, crash if they can't call -retain on their contents, so you can't make an NSArray of the root classes, because some of them do not implement the NSObject protocol. rdar://8487380 This is a not an issue in a garbage-collected environment, since objc_msgsend() eats calls to -retain, but we clearly need to support non-garbage-collected runtimes. So, we need a wrapper for the Class type. Then, the issue was what to do about metaclasses. Even the C API seems to be of two minds about the degree to which metaclasses are an implementation detail, e.g. there are separate class_getClass*() and classGetInstance*() functions, but only one class_copy*List(), which only returns things defined on the normal class, not the metaclass. I talked with @rentzsch and @jemmons, and we agreed that Objective-C coders, even if they know about metaclasses, don't think in terms of them, e.g. there is *one* conceptual NSObject class, and it has both instance and class methods.
These changes both make the runtime wrapper more and less true to the underlying API. Most importantly, they introduce a new RTClass class that wraps Class types. While you can get away with treating a Class like an Objective-C object, they are distinct structs in the headers. These changes also enable you to more easily manipulate root classes, including those that don't inherit from NSObject, e.g. NSProxy. They even help with those that don't conform to the NSObject protocol, e.g. NSMessageBuilder, NSZombie, and Object.
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These changes are rather extensive, and change some return types and semantics, breaking backward compatibility.
Why did RTMethodSendingAdditions called the rt_class method instead of the NSObject's class method?