Re: Core Data: unidirectional relationships
Re: Core Data: unidirectional relationships
- Subject: Re: Core Data: unidirectional relationships
- From: Quincey Morris <email@hidden>
- Date: Wed, 13 Feb 2008 11:59:24 -0800
On Feb 13, 2008, at 02:59, Ruotger Skupin wrote:
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
What about:
Entity: Department
Attributes: ...whatever...
Relationships:
headOfDepartment --> Role
viceHeadOfDepartment --> Role
pointyHairedBoss --> Role
dilbert --> Role
other Employees -->> Employee
Entity: Role
Attributes: ...whatever...
Relationships:
department --> Department
employee --> Employee
(add role-type attribute or subclass Role if needed)
Entity: Employee
Attributes: ...whatever...
Relationships:
department --> Department
roles -->> Role
That's basically the same as your "ugly" version, just less ugly.
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