Binding mutable to-many relationships with Core Data
Binding mutable to-many relationships with Core Data
- Subject: Binding mutable to-many relationships with Core Data
- From: minapre999 <email@hidden>
- Date: Thu, 23 Aug 2007 19:49:13 +1000
I have an App similar in concept to a database that has a Date
entity, Address entity, etc and I would like to allow have the user
to define (without limit) number of these they can have for each
"table". For example one user might define a "Start Date",
"Progress Date", "End Date", and then create records containing each
of these that can be displayed in a table view.
The problem is that Core Data doesn't allow you to append attributes
so the model needs to define these in a to-many relationship. An
example might look like this:
MyMainEntity
relationships: records <->> (to many relationship, inverse is
Record.mainEntity)
RecordEnity
attributes: nameAttribute (String attribute "Start Date",
"Progress Date", "End Date", etc)
relationships: mainEntity <->> (to one relationship, inverse is
MyMainEntity.records)
DateRecordEntity (inherits from RecordEntity)
attributes: dateAttribute
AddressRecordEntity (inherits from RecordEntity)
attributes: street, city, zip (String attributes)
I want the table to bind to the MyMainEntity arranged objects. I
want the value for each column to be the records.nameAttributes. eg
first column binds to records.nameAttributes where the nameAttribute
= Start Date, the second column binds to records.nameAttributes where
the nameAttribute = Progress Date, etc. This could probably be done
using a Fetch Predicate. However, it seems that this model could be
extremely slow for a large number of entries or a modest number of
user defined Record Entities. This is like a model of a traditional
database - I was thinking there must be an easier way to do so.
Would anyone have any suggestions ?
A second question - it would be nice to only insert the relationship
object when the user enters a value (ie is null by default, insert
when user enters a value). I have tried observing the relevant
key paths and creating it there, but it does not seem to work. Any
idea' on this is also appreciated.
thanks
CH
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