How to set up a typical users HABTM roles relationship

Question

I'm quite new to this and I'm using cancan + devise for my user auth. However I'm not really sure what it means to set up a typical users HABTM roles relationship nor do I really understand what a HABTM relationship is.

Can anyone explain it really well or point me to a good tutorial or example?

recursive · Accepted Answer · 2011-12-02T02:46:56.127

16

HABTM means has and belongs to many. You basically need a table as a middle man to track multiple id's (called a through table). When referenced as a typical users HABTM roles relationship, they really mean there would be a User model, Role model, users table, roles table, and a roles_users table. Don't forget to add the the HABTM -- roles_users -- table. A typical setup follows:

class User < ActiveRecord::Base
  has_and_belongs_to_many :roles
end

class Role < ActiveRecord::Base
  has_and_belongs_to_many :users
end

You can then use the associations like normal saying User.first.roles and Role.first.users.

There are also a couple Railscasts on your issues.

edited Dec 02 '11 at 02:46

answered Jul 14 '11 at 08:02

recursive

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how do you create the users_roles table? – Vasseurth Jul 14 '11 at 08:11
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`rails g migration add_users_roles_table` – recursive Jul 14 '11 at 08:18
Sorry, hit enter too soon, edit the above with the following information: [gist](https://gist.github.com/1082098). Then run `rake db:migrate`. That should do it. – recursive Jul 14 '11 at 08:23
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@recursive shouldn't it be `rails g migration add_roles_users_table` ? I thought Rails expects the 2 models to be in alphabetical order – Arcolye Nov 28 '11 at 05:53

score 3 · Answer 2 · answered Jul 14 '11 at 07:13

3

The Ruby on Rails Guides are a good starting point here also this tutorial is exactly what you want

answered Jul 14 '11 at 07:13

John Beynon

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I'm using the second tutorial, but it just says, 'set up a HABTM relationships' doesn't say how – Vasseurth Jul 14 '11 at 07:22
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http://mikewilliamson.wordpress.com/2010/07/02/rails-has_and_belongs_to_many/ - simple tutorial on habtm – Bohdan Jul 14 '11 at 07:24
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Most of the have a UsersHaveAndBelongToManyRoles migration, how do you generate that? – Vasseurth Jul 14 '11 at 07:47
The docs are ridiculously vague on this...Ugh. Thanks for the tutorials. – Ruben Martinez Jr. Jun 05 '14 at 16:51

How to set up a typical users HABTM roles relationship

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