Re: Fetching the data of a many-to many relationShip

On Jul 2, 2009, at 6:26 AM, Gustavo Pizano wrote:

On Thu, Jul 2, 2009 at 11:48 AM, David Avendasora <email@hidden> wrote:

On Jul 2, 2009, at 5:19 AM, Gustavo Pizano wrote:

Hello.

I have the following:

I have a Entity called WG, and one called, TRANSLATIONSET. so the relationship is WG << >> TRANSLATIONSET.

if I have the wg , I want to get all the TRANSLATIONSET that this partigual wg has. Whne I was definiyng the EOModel, I set up a manytomany relationship with a join table called WGxTS and I unchecked the Flattern box, I read it somewhere.

If all the WGxTS table is doing is being a join table for a many-to-many relationship, then flattening it I believe is the right thing to do.

mmmm I see.
 

so if I do.

NSArray aux = wg.toTranslationSets();

If you don't do flattening, then you'd need something along the lines of: wg.toTranslationSets().valueForKey("TranslationSet")

oops.. I guess I'll have to go back to the theory,... didn'gt get why the valueForKey .. I guess its becuase each WGxTS has the TranslationSet_KEY and WG_KEY so geting the values for those kesy will create the proper swl command and fetch the right data.. isn't it?

RIght. If you aren't flattening, then when you call wg.toTranslationSets() all you are going to get are EOs that represent the join table (they are valid EOs, they just don't have much "business" meaning. 

Since the join table EOs will have to-one relationships to TranslationSet and WG, then you have to call the relationship to get the actual object you are looking for. So, the exact syntax would be

NSArray<TranslationSet> aux = wg.toTranslationSets().valueForKey(WGxTS.TranslationSet_KEY);

Of course, if you turn flattening back on, it would simply be:

NSArray<TranslationSet> aux = wg.translationSets();

Much cleaner and easier to understand. Actually, if you don't turn flattening back on, I'd manually flatten it by writing cover methods for the relationships such as (on the WG entity):

public NSArray<TranslationSet> translationsSets() {

NSArray<TranslationSet> aux = wg.toTranslationSets().valueForKey(WGxTS.TranslationSet_KEY);

}

Dave

Dave

the contents of aux are all what is in the WGxTS which is not more than the pk of WG and TRANSLATIONSET related..

What am I missing here, this is the first time Im working with many-to-many rs.


Thanks in advance

Gustavo

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