GLORP - RelationshipMapping

Hi,
        i'm new with GLORP (and smalltalk), i'm having a problem to build a
"RelationshipMapping" between my tables, perhaps you could help me.

I have the following DB structure:

EVENT -> [event_id,..]
PARTICIPANT -> [participant_id, event_id,...]
PARTICIPANT_OPTION_LINK -> [id_option, id_participant]
OPTION -> [option_id,option_value(text)]

I need to be able of fetch the PARTICIPANT options FROM the Participant
Object.

i'm trying to do something like the code below in my descriptor, and i'm
getting the following exception: (Unhandled exception: Joins should go
from the table(s) associated with this descriptor to the other
table(s)).

do you have any suggestion of how could i do this relationship works ?

Thank you,
Armando Perico

(aDescriptor newMapping: Glorp.RelationshipMapping)
                attributeName: #options;
  referenceClass: Option;
                usesLinkTable: true;
        mappingCriteria: (Glorp.Join
    from: ((self tableNamed: 'PARTICIPANT') fieldNamed: 'ID')
    to: ((self tableNamed: 'PARTICIPANT_OPTION_LINK') fieldNamed:
'ID_PARTICIPANT'));
                targetTableJoin: (Glorp.Join
    from: ((self tableNamed: 'PARTICIPANT_OPTION_LINK') fieldNamed:
'ID_OPTION')
    to: ((self tableNamed: 'OPTION') fieldNamed: 'ID'));






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The message is being pretty precise in telling you what's wrong. That join isn't going from and to the places that Glorp expects it to. But the reason is that #targetTableJoin: is not what you are thinking it is. See the method comment. "This is *NOT* supposed to be a join from the link table to the target table. That's reverseJoin, and is calculated automatically."

But basically, if you have foreign key constraints defined for your link table, the answer is to delete everything after "usesLinkTable: true" and just let Glorp figure out the join automatically. If the join is ambiguous, you can just specify the join from the source table to the link table. The rest can normally be computed automatically. And in most cases, all of it can be computed automatically.

At 02:48 PM 2010-03-31, Armando Perico wrote:

Hi,
        i'm new with GLORP (and smalltalk), i'm having a problem to build a
"RelationshipMapping" between my tables, perhaps you could help me.

I have the following DB structure:

EVENT -> [event_id,..]
PARTICIPANT -> [participant_id, event_id,...]
PARTICIPANT_OPTION_LINK -> [id_option, id_participant]
OPTION -> [option_id,option_value(text)]

I need to be able of fetch the PARTICIPANT options FROM the Participant
Object.

i'm trying to do something like the code below in my descriptor, and i'm
getting the following exception: (Unhandled exception: Joins should go
from the table(s) associated with this descriptor to the other
table(s)).

do you have any suggestion of how could i do this relationship works ?

Thank you,
Armando Perico  

(aDescriptor newMapping: Glorp.RelationshipMapping)
                 attributeName: #options;
                 referenceClass: Option;
                 usesLinkTable: true;
         mappingCriteria: (Glorp.Join
                          from: ((self tableNamed: 'PARTICIPANT') fieldNamed: 'ID')
                          to: ((self tableNamed: 'PARTICIPANT_OPTION_LINK') fieldNamed:
'ID_PARTICIPANT'));
                 targetTableJoin: (Glorp.Join
                          from: ((self tableNamed: 'PARTICIPANT_OPTION_LINK') fieldNamed:
'ID_OPTION')
                          to: ((self tableNamed: 'OPTION') fieldNamed: 'ID'));






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