Dictionaries doesn't do deepCopy, but they do support NSCoding. Do you think you can use serialization to a NSData (a memory block) instead? It will have other benefit when you have too much undo items and want to page to a file. ;)
-Jonny 在 2012-7-23，下午9:12，Andreas Grosam <[email protected]> 写道： > > On 23.07.2012, at 14:04, Mike Abdullah wrote: > >> >> On 23 Jul 2012, at 12:57, Andreas Grosam <[email protected]> wrote: >> >>> >>> On 23.07.2012, at 13:09, Mike Abdullah wrote: >>> >>>> Aha, now we're talking. You want -initWithDictionary:copyItems: >>> >>> No, this is not a deep copy. >>> >>> Suppose, there is an element within the array, whose value is a mutable >>> dictionary. If I change the that mutable dictionary (or its values), the >>> copy and the dictionary would still compare equal to the copy (since >>> children haven't been copied). >>> >>> >>> Thus, I need to define a deepCopy method for NSDictionary (and NSArray, >>> too). >> >> You should seriously consider whether your design is a good idea then. >> Copying the objects in an array is rare, but justifiable. Having multiple >> levels of nested dictionaries is rarely so. Sure you're not (ab)using >> dictionaries to avoid defining a new class? > > No, I don't think so. The NSDictionary/NSMutableDictionary is completely > suitable for the purpose to represent that object which I have here. There is > just no method to create a deep copy. (On the other hand, the isEqual method > will effectively "deep" compare.) > > So, you might wonder why there is a need to have a deep copy? Well, how can I > answer this without digressing? ;) > > But as an example: > > Suppose, there is a quite rich object represented as JSON. The JSON will be > parsed and represented as a Foundation object, which is a NSDictionary. This > is my object. Now suppose, there is the possibility to edit and make changes > to this deep leveled object. Before making any changes in a GUI, I need to > create a "Momento" (see, wiki <http://en.wikipedia.org/wiki/Memento_pattern> > in order to save state of the original object and possibly be able to revert > changes. > > Due to the lack of attributes attachable to properties in Objective-C > language and a momento method (I already warned that I'll possibly digressing > ;) ) I just use a deep copy for creating the momento. > > Sure, I could use CoreData for accomplishing this as well … but this was > just an example. > > > > > _______________________________________________ > > Cocoa-dev mailing list ([email protected]) > > Please do not post admin requests or moderator comments to the list. > Contact the moderators at cocoa-dev-admins(at)lists.apple.com > > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/cocoa-dev/yingshen.yu%40gmail.com > > This email sent to [email protected] _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
