NSArray是

NSArray is a class cluster. This basically means that NSArray objects could be made up of one of several different actual implementations and __NSCFArray is one of the classes (probably the most common) that NSArray can use to implement an array.

只需像使用其他NSArray一样使用__NSCFArray，它将正常工作.

Just use the __NSCFArray as you would any other NSArray and it'll work fine.