Replacing the ID with the value

rubyonrails-talk
1

Hi. I have a project based on Rails 3.0.3 and MySQL.

There are 2 tables (not all columns shown):

1. users (id, name, group_id)

class User < ActiveRecord::Base   belongs_to :groups end

2. groups (id, name)

class Group < ActiveRecord::Base   has_many :users end

Console output:

irb(main):001:0> User.first => #<User id: 1, name: "John Smith", group_id: 3>

How can i do that besides the "group_id: 3" result the query will return the Group name too. For example:

irb(main):001:0> User.first => #<User id: 1, name: "John Smith", group_id: 3, group: "Administrator">

I can do this by using the JOIN statement in mysql, but i need to use raw sql queries. May be there is a way to do it by using ActiveRecord style ?

2

Have a look at the documentation: http://ar.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

"Eager loading" is probably your friend, but you can also do what you want by changing the :select option of any AR query.

3

Hi. I have a project based on Rails 3.0.3 and MySQL.

There are 2 tables (not all columns shown):

1. users (id, name, group_id)

class User < ActiveRecord::Base belongs_to :groups

That should be :group (singular), user belongs to one group so singular.

end

2. groups (id, name)

class Group < ActiveRecord::Base has_many :users end

Console output:

irb(main):001:0> User.first => #<User id: 1, name: "John Smith", group_id: 3>

How can i do that besides the "group_id: 3" result the query will return the Group name too. For example:

You can just say User.first.group.name or user = User.first group_name = user.group.name

Rails will fetch the group from the database when you reference it. Alternatively you may use the :include option on find to force it to fetch the user and group in one query if you are running into performance problems.

Colin