Can a cftyperef really be a cfstringref?
So a CFTypeRef could really be a CFStringRef, or a CFNumberRef, or a CFDictionaryRef, or anything else. So if that CFTypeRef is actually a CFDictionaryRef, just as an example, what would you want as the result?
Is there an API to tell the mutability of a cfstringpointer?
No “public” API is provided to tell the mutability of a CFStringpointer (or mutability of any type). Combined with Toll-Free bridging, this meant that you could mutate immutable NSStringobjects, even though the NSMutableStringAPIs did perform a mutability check and caused “some kind of problem” when trying to mutate an immutable object.
When to call cfdatarefobject with Nullpointer?
This action is called with a CFDataRefobject when new data becomes ready to process. This action returns a CFDataRefcontaining the results. When this action receives a NULLpointer as its input, it means that either the caller or a transform earlier in the chain has indicated that it will pass no further data.