Re: Core Data: unidirectional relationships
Re: Core Data: unidirectional relationships
- Subject: Re: Core Data: unidirectional relationships
- From: William Turner <email@hidden>
- Date: Wed, 13 Feb 2008 09:52:23 -0800
Hi Ruotger,
Another alternative that might work for you is to add a
"title" (string) attribute to Employee and fetched properties to the
Department for each of headOfDepartment, viceHeadOfDepartment,
pointyHairedBoss, and dilbert, with their predicates being
title=="Head", title=="ViceHead", etc.
You can read more about using fetched properties to represent one-way
relationships near the end of http://developer.apple.com/documentation/Cocoa/Conceptual/CoreData/Articles/cdRelationships.html
Wil
On Feb 13, 2008, at 9:29 AM, Brian Williams wrote:
I have had to deal with this also. I think that the best solution is
to just
have those empty back links and accept the clutter. You could also
have
subclasses of employee, but i am sure that would cause other problems.
On 2/13/08, Ruotger Skupin <email@hidden> wrote:
Hi,
consider the following example (that what I would like to model):
Entity: Department
Attributes: ...whatever...
Relationships:
headOfDepartment --> Employee
viceHeadOfDepartment --> Employee
pointyHairedBoss -->
dilbert -->
other Employees -->>
Entity: Employee
Attributes: ...whatever...
Relationships:
department --> Department
Every Employee is only in one Department. The Department has (and
needs) four special Employees (head, vice head, pointy haired boss,
dilbert). Turns out that it is impossible to model this with
bidirectional relationships if you don't want to model it like that:
Entity: Employee
Attributes: ...whatever...
Relationships:
departmentImHeadOf --> Department
departmentImViceHeadOf --> Department
departmentImPointyHairedBossOf --> Department
departmentImDilbertOf --> Department
departmentOtherEmployeeOf --> Department
The other alternative is to model it with unidirectional
relationship,
which is discouraged.
Can anyone gime some advice on this?
Ruotger
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