Re: Many-to-many question ...
Re: Many-to-many question ...
- Subject: Re: Many-to-many question ...
- From: "Daniele Corti" <email@hidden>
- Date: Thu, 25 Oct 2007 11:37:43 +0200
2007/10/25, Lachlan Deck <email@hidden>:
On 25/10/2007, at 6:43 PM, Daniele Corti wrote:
> 2007/10/25, Lachlan Deck <email@hidden>:
>>
>> On 25/10/2007, at 11:17 AM, Shagor Ghani wrote:
>>
>>> Have a quick question around join tables storing M2M
>>> relationships. I need
>>> to store a M2M relationship and created a table for it using
>>> Property>Join
>>> in Many-to-Many option from within EOModeler itself. This table
>>> has two
>>> columns, id1 and id2, both of which are primary and which together
>>> produce a
>>> unique record. In my code, I've been doing creating new rows into
>>> this
>>> table using the standard
>>> object.addObjectToBothSidesOfRelationshipWithKey(
>>> object, key ) call. Now, though, I also need to store additional
>>> values
>>> within this record, for example a boolean bit indicating whether
>>> the record
>>> is active or not. How is this done? If I manually add a 3rd
>>> attribute
>>> column, what call is then used to update/create new record(s)?
>>
>> You have two choices with M2M Join tables.
>> A<-->>AB<<-->B
>>
>> 1) flatten the relationships... so that you're adding to both sides
>> of relationship two records on either side of the join. Join records
>> using EOGenericRecord and don't have any logic in them.
>>
>> A myA = (A)EOUtilties.createAndInsertInstance(ec, "A");
>> B myB = (B)EOUtilties.createAndInsertInstance(ec, "B");
>> myA.addObjectToBothSidesOfRelationshipWithKey(myB, "bs");
>
> How this work? Do you need to set the EOmodel in some way?
Flattening relationships involves creating a many-to-many join like
here:
http://wiki.objectstyle.org/confluence/display/WOL/Creating+a+Many+to
+Many+Join
Thank you, but is there a way in EOModeler? (really, I've never completely understand how to user Entity Modeler)
> 2) don't flatten the relationships
Otherwise, create normal toMany relationship from A to AB, and B to
AB in the modeler.
Usually I use this , but I like to continue learning new way to do things ;-P
with regards,
--
Lachlan Deck
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Daniele Corti
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