Re: Mapping Model
Re: Mapping Model
- Subject: Re: Mapping Model
- From: Keary Suska <email@hidden>
- Date: Mon, 23 Aug 2010 12:43:20 -0600
On Aug 23, 2010, at 11:06 AM, Amy Heavey wrote:
> Hi,
>
> I've got a core data app that I'm working on, and I started off with quite simple relationships. I've got a products entity, and a purchase order entity, which had many to m any relationships between them. I now need to be able to set a quantity for each product in each purchase order. I think I need to set up an inbetween entity, (called purchaseOrderItem) which stores the quantity for each product, and has relationships to the product and purchase order entity.
>
> I can set it all up in the datamodel, but to be able to use the data already in the app I need to migrate it over. I expect to initially set all quantites to 1, but I can't work out how to set up the mapping model so it moves the relationships correctly.
>
> Can anyone point me in the right direction?
>
> data model 1.0
> Entities: Product, PurchaseOrder
> Relationships: Product <<---->>PurchaseOrder
>
> data model 1.1
> Entities: Product, PurchaseOrder, PurchaseOrderItem
> Relationships: Product <---->> PurchaseOrderItem
> PurchaseOrderItem <<----> PurchaseOrder
I wouldn't change the existing relationship(s)--create new ones instead. You will have to subclass NSEntityMigrationPolicy to create appropriate "PurchaseOrderItem" relationships from the "Product" relationships.
Have you read this doc:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmMigrationProcess.html#//apple_ref/doc/uid/TP40005508-SW4 ?
HTH,
Keary Suska
Esoteritech, Inc.
"Demystifying technology for your home or business"
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