On 27/02/2011, at 17.19, Joanna Carter wrote: > Le 27 févr. 2011 à 15:25, Mikkel Eide Eriksen a écrit : >> It would only return nil in some cases. I'm working on some Gedcom <-> Core >> Data code. All objects in Gedcom have a "tag" identifier. One such object is >> an "Event", with the generic tag EVEN. There are multiple subtypes of Event, >> such as BIRT (birth), DEAT (death), CONF (confirmation), etc. >> >> An Event can also have a "type", which in the case of generic EVENs is >> something for which no specific tag exists. So: >> >> Event with type "Birth" should become: >> 1 BIRT >> 2 DATE ... >> 2 PLAC ... >> >> generic Event with some type should become: >> 1 EVEN >> 2 TYPE Event Type >> 2 DATE ... >> 2 PLAC ... >> >> My current implementation of the type getter on the Event object checks to >> see if the type is one of the known tags (Birth, etc), and returns nil so as >> to avoid redundant data: >> >> 1 BIRT >> 2 TYPE Birth >> 2 DATE ... >> 2 PLAC ... >> >> I think I'll probably use a displayType property for bindings, and the >> internal type property for writing out to Gedcom. Another option would be to >> subclass Event into all the different types, but that seems overkill. > > If you are displaying the event's "tag", then all you need is to return the > appropriate string; the event getter can check what to return. > > But, if you are transforming to/from an event from/to something else that > should contain the tag value, then what about using a variation of the > Visitor design pattern? > > Are you creating something from the event, or an event from something else? > Can you let us see an idea of the two classes involved?
I do both. I create the event from gedcom data, and create gedcom data from the event. http://code.google.com/p/cocoa-gedcom/wiki/Design The "type" code in question is below: http://code.google.com/p/cocoa-gedcom/source/browse/trunk/GCCoreData/src/GCEvent.m#247 When creating gedcom data, it is accessed via GCEvents superclass GCObject: http://code.google.com/p/cocoa-gedcom/source/browse/trunk/GCCoreData/src/GCObject.m#380 Since the tagDict is built dynamically at runtime, I should mention it looks like this: { key = type; tag = TYPE; type = attribute; } Which means the actual part of gedcomNode that executes is lines 411+. Note that almost all attributes are simply written out as-is, it's only for the specific case of an Event which has a type that means the same thing as its tag that I don't want the value. I just now added a displayType, and this works (I can show "Birth" in the GUI and nothing in the Gedcom data), but as I mentioned it doesn't seem so clean to have two ways of accessing the same primitiveType. Regards, Mikkel
smime.p7s
Description: S/MIME cryptographic signature
_______________________________________________ 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
