Question

From the image below.

It can be seen that I have three table User, User_group and group. I am trying to link a user to user_group and Group to user_group in other words link a user to a user_group. Currently in my user model I have the following:

User.rb
has_and_belongs_to_many :group

Group.rb
has_and_belongs_to_many :user

What I am basically trying to do is import the data into the User_group table. What is the best way around this. Tried searching online and have had no luck.

Form Layout

The user should be able to assign themselves to a group. When they click update the information entered should be saved to the user_group table

Answer 1

If you want to use the Rails convention, you should name your tables users, groups and groups_users and change:

has_and_belongs_to_many :group
has_and_belongs_to_many :user

to:

has_and_belongs_to_many :groups
has_and_belongs_to_many :users

If you want to keep the table names you described above, you have to do the following:

class User < ActiveRecord::Base
  set_table_name 'USER'
  has_and_belongs_to_many :groups, :join_table => 'USER_GROUP'
end

class Group < ActiveRecord::Base
  set_table_name 'GROUP'
  has_and_belongs_to_many :users, :join_table => 'USER_GROUP'
end

Note that table names are case sensitive. I used upper case, but that probably does not match your situation.