Re: valueForKey for Relationship?
Re: valueForKey for Relationship?
- Subject: Re: valueForKey for Relationship?
- From: James Cicenia <email@hidden>
- Date: Thu, 2 Sep 2004 16:14:10 -0500
perfect! The return of Object felt singular. I am not a complete OO
person yet.
By the way I just got the book!!!! Excellent.
-James
On Sep 2, 2004, at 3:19 PM, Colin Clark wrote:
Hi James,
As is, valueForKey() will return relationships. If you look at the
signature for valueForKey, it returns an object of type Object,
meaning that it can return anything. If you call something like
valueForKey("projects") on an EO with a to-many "projects"
relationship, you'll get an NSArray of EOs back.
Think about how KVC works for a moment. In essence, when you pass it a
key such as "projects," it uses Java reflection to look for a method
defined on your EO called getProjects(). valueForKey() will
dynamically return whatever object that method is defined as returning
(casted back to an Object). So, if your getProjects() method is a
to-many relationship accessor and returns an NSArray, KVC will pass
you back that array. This is a simplified explanation, so you'll want
to look at the documentation for a better explanation of how KVC
actually works.
Don't forget valueForKeyPath()--defined in
NSKeyValueCodingAdditions--which allows you to specify full key paths.
For example, valueForKeyPath("projects.projectManager.name") will
automatically follow the relationships specified by the key path and
pass you back the project manager's name. Nice.
Colin
On Thursday, September 2, 2004, at 03:50 PM, James Cicenia wrote:
Is there a variant, I haven't found it in the api yet, that returns
an array of related objects based upon the key?
-James Cicenia
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---
Colin Clark
Dynamic Web and Database Development Lead,
Resource Centre for Academic Technology,
University of Toronto
(416) 946-7592 / email@hidden
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