Comments on: Grails Extended ManyToMany GORM Example

By: Trying not to be gormless with GORM « All things Grails and RIA

Trying not to be gormless with GORM « All things Grails and RIA — Sun, 04 Apr 2010 15:51:51 +0000

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By: Jeff

Jeff — Tue, 10 Jun 2008 16:50:12 +0000

hey take a look at the documentation:
http://grails.org/GORM+-+Defining+relationships

it explains the magic of addTo* much better than I did.

Going forward with my example I’m more interested in creating a many to many relationship where the join table can have extra columns.

By: AnotherHale

AnotherHale — Tue, 10 Jun 2008 05:02:22 +0000

I am new to Grails/Groovy and not familiar with much of the syntax yet. I am wondering if I can do the following.

In the Characteristic class can you replace these two methods:

List addToPeople(Person person)
List removeFromPeople(Person person)

with the following:

List addPerson(Person person)
List removePerson(Person person)

It just seems more intuitive to code charcteristic.addPerson(someperson). I just don’t know if there is something magical about ‘addTo*’ or ‘removeFrom*’

By: andhapp

andhapp — Sat, 07 Jun 2008 17:06:42 +0000

I got stuck in the same thing as well… I had my hibernate mapping files ( *.hbm.xml) and I set the inverse to false on both sides of the relationship for the many to many to work… i noticed that if you do not do that it would not save the object (or the values) in the linking table for some reason.

By: Jeff

Jeff — Sat, 07 Jun 2008 15:40:11 +0000

I found the official documentation example today, which is very clear. Thanks for the tip Graeme.

By: Graeme Rocher

Graeme Rocher — Sat, 07 Jun 2008 10:02:39 +0000

Also note the article (http://grails.org/Many-to-Many+Mapping+without+Hibernate+XML) is a tutorial written by a Grails user and not official documentation. You don’t need to setup an OpenSessionInViewFilter, grails does this for you

By: Graeme Rocher

Graeme Rocher — Sat, 07 Jun 2008 10:01:17 +0000

class Person {

static hasMany = [characteristics:Characteristic]

…
}

class Characteristic {

static hasMany = [people:Person]
static belongsTo = Person
…
}

Cheers
Graeme