Re: mutually exclusive 1-to-0 or 1 relationship modeling
Re: mutually exclusive 1-to-0 or 1 relationship modeling
- Subject: Re: mutually exclusive 1-to-0 or 1 relationship modeling
- From: Michael Gargano <email@hidden>
- Date: Fri, 14 Jan 2011 10:04:51 -0800
- Acceptlanguage: en-US
- Thread-topic: mutually exclusive 1-to-0 or 1 relationship modeling
The only question I have on this method is how do I propagate the primary key now? If the modeler thinks it's a 1-to-many I can't check that box. That's how this started to begin with. I had them set as one-to-manies, but I didn't know how that pk should be propagated in code.
On Jan 14, 2011, at 11:45 AM, Kieran Kelleher wrote:
> one-to-one relationships can only be mandatory, and EOF *automatically* creates the B and C when you create A and propogates the primary key (a setting in the EOModel BTW) from A to B and A to C.
>
> The only way to set up an optional "1-to-1" is to create a 1-to-many in EOF,
>
> A <-->> B
> A <-->> C
>
> and put methods in A to get and set singular B or C, returning null when empty toMany array.
>
> Enforce the zero or one count on the relationship in the database by making the foreignkey of A a unique index in tables B and C.
>
> The mutually exclusive rule can be checked in validateForSave.
>
> YMMV,
>
> Kieran
>
> On Jan 14, 2011, at 11:16 AM, Michael Gargano wrote:
>
>> I have three entities A, B, and C...
>>
>> A has a 1-to-0 or 1 with B
>> and
>> A has a 1-to-0 or 1 with C
>>
>> An entry in A either has an entry in B or an entry in C. The two are mutually exclusive. When I try to set this up in the modeler it gives me some problems. Once I set a relationship as a one-to-one, the modeler won't let me select optional if optional is already unselected and the modeler generates a warning about having optional set if I edit the plist directly. I'm not sure if I'm doing this correctly, but it looks to me like the modeler isn't allowing 1-to-0 or 1 relationships.
>>
>> So, if I just live with the warnings...
>>
>> If I set the relationship between A and B and set the relationship to C to null (again because B and C are mutually exclusive), when I save changes it throws an exception complaining that all the properties in B are null. Anyone else doing something like this?
>>
>> Thanks.
>> -Mike
>>
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