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the message copy to an existing instance. Copying a channel will mean that its title ,
infoString , and items array are copied into a new instance of RSSChannel .
Now, you may be thinking, “If you copy the items array, aren't you just duplicating all
of the RSSItem s in it?” Nope. An array only keeps references to the objects that it con-
tains, so by copying an array, you are just copying the addresses of each object into the
new array, not the objects themselves ( Figure 29.6 ).
Figure 29.6 Copying an RSSChannel
In RSSChannel.h , declare that this class conforms to NSCopying .
@interface RSSChannel : NSObject
<NSXMLParserDelegate, JSONSerializable, NSCoding , NSCopying >
 
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