Hi all - I'm working on an app that has the concept of allowing the user to create templates of things which are then instanced into a document. Central to this is the idea that the user can create a template, then select it as part of another template or an instance. The relationship between template types is fixed. (For example, suppose one template is a tire and another is a car; the car has a link to a tire template; the user can select the 17" tire template for the car they are working on.)
I have an NSTableView with NSComboBoxCell's which contain lists of the other appropriate templates the user has created, which can be linked to the current template. The problem I'm having is that, if I put the templates the user can choose from into an array controller and source the combo box from that, the control wants the template to have implemented NSCopying, and then makes copies of it to render. A copy of the template is what ends up getting put back into the base template model object's pointer. So base template ends up referring to the other template by value, not by reference. This is a problem for me, as the expectation being set is that editing the template also affects the instances derived from it (to carry the car analogy forward, if the user uses the 17" tire template on three cars, then changes the tread pattern on the tire, that should affect those three cars with no further action.) I've come up with two possible solutions, neither of which I like. One is to use the template's name as a key; that's ugly, the app currently doesn't have the restriction that template names have to be unique (though that's not an entirely unreasonable limitation). The other is to wrap the model class in a proxy that DOES implement NSCopying, but just contains a single pointer to the template instance. That's ugly since then I have to code and maintain another layer of indirection between the controller and the model. Is there a standard pattern for dealing with this situation? Thanks!! _______________________________________________ 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
