How to handle Many-To-Many In Grails without belongsTo?

Posted by nute on Stack Overflow See other posts from Stack Overflow or by nute
Published on 2010-05-05T17:13:50Z Indexed on 2010/05/05 17:18 UTC
Read the original article Hit count: 213

Filed under:

grails

|

many-to-many

I need to create a many-to-many relationship in Grails.

I have a "Question" domain and a "Tag" domain. A Question can have 0 or more tags. A Tag can have 0 or more Questions.

If I put a "hasMany" on each sides, it gives me an error saying I need a "belongTo" somewhere. However, adding a belongsTo means that the owner must exist...

Like I said, a Tag could have 0 questions, and a Question could have 0 tags. There is no concept of an owner, it's a many-to-many!

What am I supposed to do?

© Stack Overflow or respective owner

Related posts about grails

Grails, app-engine, jpa - beginner having trouble with grails generate-all

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to learn about grails with Google App Engine and JPA by following a few tutorials: http://www.morkeleb.com/2009/08/12/grails-and-google-appengine-beginners-guide/ http://inhouse32.appspot.com/index.html http://grails.org/plugin/app-engine I've got grails 1.3.0 RC 2, and App Engine SDK… >>> More
Grails Warnings/Errors during run-app

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm currently seeing the warnings below when trying to run my Google App Engine/Grails test app in Eclipse. Warning, target causing name overwriting of name startLogging Warning: C:\Users\Some Person.grails\1.2.0\projects\test-grails\plugins\app-engine-0.8.8\grails-app\conf\spring not found. Warning:… >>> More
Grails, app-engine, jpa - TargetInvocationException

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to learn about grails with Google App Engine and JPA by following a few tutorials: http://www.morkeleb.com/2009/08/12/grails-and-google-appengine-beginners-guide/ http://inhouse32.appspot.com/index.html http://grails.org/plugin/app-engine I've got grails 1.3.0 RC 2, and App Engine SDK… >>> More
Inject log object in Grails class outside of grails-app

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a class in src/groovy in my grails project. How do i make a log field that gets injected with the correct logger for that class ? Is there a commons logging or just log4j in grails ? >>> More
grails run-war connects to mysql but grails run-war doesn't

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I have a unexpected problem. I had create a war with grails war. Then I had deployed in Tomcat. For my surprise the crud works fine but I don't know what persistence is using. So I did this test: Compare grails prod run-app with grails prod run-war. The first works fine, and does conect with… >>> More

Related posts about many-to-many

Self referencing symmetrical Hibernate Map Table using @ManyToMany

as seen on Stack Overflow - Search for 'Stack Overflow'
I have the following class public class ElementBean { private String link; private Set<ElementBean> connections; } I need to create a map table where elements are mapped to each other in a many-to-many symmetrical relationship. @ManyToMany(targetEntity=ElementBean.class) @JoinTable( … >>> More
Django ManyToMany join query

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm sure this is really simple, but I can't for the life of me find any documentation explaining how to do this. How do I get the results of a ManyToMany field inside a join as opposed to doing this: {% for tag in article.tags.all %} Which results in an extra query? What I'd like to do is fetch… >>> More
django ManyToMany through help

as seen on Stack Overflow - Search for 'Stack Overflow'
Hay I've got a question about relationships. I want to Users to have Friendships. So a User can be a friend with another User. I'm assuming i'll need to use the ManyToManyField, through a Friendship table. But i cannot get it to work. Any ideas? Here are my models. class User(models.Model): … >>> More
Limiting choices from an intermediary ManyToMany junction table in Django

as seen on Stack Overflow - Search for 'Stack Overflow'
Background I've created three Django models—Inventory, SalesOrder, and Invoice—to model items in inventory, sales orders for those items, and invoices for a particular sales order. Each sales order can have multiple items, so I've used an intermediary junction table—SalesOrderItems—using the through… >>> More
What's best practice to check if an object is part of a ManyToMany relationship in Django

as seen on Stack Overflow - Search for 'Stack Overflow'
from an instance of Site with a ManyToMany relationship to Kiosk, i'd like to check if a Kiosk object is part of the relationship. I could do self.apps.get(id=app_id).exists() and check if True or self.apps.get(id=app_id) and catch the ObjectDoesNotExist error or self.apps.filter(id=app_id)… >>> More