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Re: Inverse to-one relationships
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Re: Inverse to-one relationships


  • Subject: Re: Inverse to-one relationships
  • From: Paul Hoadley <email@hidden>
  • Date: Fri, 23 Jul 2010 07:26:22 +0930

Hi David,

On 23/07/2010, at 6:33 AM, David Avendasora wrote:

> I'm not 100% clear on how this is modeled.
>
> 1) Does the A.b() relationship propagate PKs?

No.

> 2) Are you saying that the A.b().a() may be null?

No, never.  A.b().a() would always give A.

> In other words, are you saying A.fetchAllAs().valueForKey(B_KEY) may not return an Array with the same objects that B.fetchAllBs(ec, B.A.isNotNull()) ?

No, I'm not saying that.  Those two expressions would return the same objects.

Sorry, I should have tried to be clearer.  Basically, I've got a parent object B (which will always be created first).  At some point, B may obtain at most one child A, but it doesn't necessarily.  So every B has zero or one child As.  Every A has exactly one parent B.

Currently I have a mandatory to-one relationship from A to B (so A knows its parent directly).  To avoid some fetching, I have added an optional to-one relationship from B to A, so B knows its child if it has one.  I assume there's no way to make these relationships inverses from EOF's perspective, and that I will just need to be careful about always setting the B to A relationship on creation of an A.


--
Paul.

http://logicsquad.net/


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References: 
 >Inverse to-one relationships (From: Paul Hoadley <email@hidden>)
 >Re: Inverse to-one relationships (From: David Avendasora <email@hidden>)

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