Hi Ken, On Jan 15, 2011, at 7:36 AM, Ken Ferry wrote:
> I'm not sure this has been made clear: It is intentional that it is > difficult to determine whether a dictionary is mutable. > > That's because you shouldn't do it. Whether a dictionary is mutable _to_you_ > is a matter of what's in the header for the method you obtained it from. > > Suppose that some object keeps a mutable array as its internal state. It > also has an accessor that lets you look at the array as an immutable array. > If you introspect it and realize its mutable, is it safe to mutate? No! > It's part of the object's internal state, you cannot just mess with it. > > It is unsafe in general to introspect mutability. > > -Ken > Cocoa Frameworks It makes sense what you're saying because introspecting an object bypassing its accessors would break encapsulation. From the client's perspective this is very clear: use the methods provided and don't mess with the internals. Roger that. However, how about the other way around? Say you have the same class you mentioned. Internally, it has a mutable array which one can manipulate via dedicated accessors. This object has an init method which accepts an array as input. The client is (should?) be free to pass an immutable or mutable array with values. I see at least two ways to honor this input and initialize the object: 1) add the input objects to the internal array (i.e. - (void)addObjectsFromArray:(NSArray *)otherArray) 2) assign the mutable version of the input array to the internal array (i.e. internalArray = [theInputArray mutableCopy]) In case of #2, (perhaps mistakenly) I was attempting to check whether it was necessary to mutate an already mutable array. It just seemed like the right thing to do: figure out whether the input array is mutable, if it isn't then make it mutable. Then proceed to set the array as the object's contents. However, since this init process is called once, perhaps it just makes sense to always call mutableCopy and be done regardless of the input type. Would this be the right approach perhaps? My main concern is how to deal with this mutability/non-mutability from the inside, not the outside. Thanks for the help, -- Tito _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) 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: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
