Rails 4 - how to use "belongs_to" on the same model twice (once with using "foreign_key")?

Question

I have a model Message:

class Message < ActiveRecord::Base
  belongs_to ...
  belongs_to ...
  belongs_to :user

  belongs_to :user,  class_name: "User",  foreign_key: "accepted_denied_by_user_id"
end

With this setup, if I call:

message.user.email

I get email of the user who accepted the message, but not who sent it.

If I remove this line:

 belongs_to :user,  class_name: "User",  foreign_key: "accepted_denied_by_user_id"

and call:

message.user.email

I get the email of a user who sent out the message.

How can I get the email of the sender and also the recipient?

I tried

message.accepted_denied_by_user.email

but this leads to

undefined method `accepted_denied_by_user' for ...

Thank you.

why you need to use `belongs_to :user` twice? It is not a good practice. Because you repeating the code which is not DRY. — Mohammad Shahadat Hossain, Mar 13 '16 at 17:49
check this http://stackoverflow.com/questions/5294775/same-model-for-two-belongs-to-associations — Arvind, Mar 13 '16 at 17:55

score 1 · Answer 1 · answered Mar 13 '16 at 17:52

It should be like this:

belongs_to :user

belongs_to :accepted_denied_by_user,  class_name: "User",  foreign_key: "accepted_denied_by_user_id"

Now you should be able to call both message.user.email and message.accepted_denied_by_user.email for specific cases.

score 1 · Accepted Answer · answered Mar 13 '16 at 17:53

You need to name the second association with different name:

belongs_to :denied_user,  class_name: "User",  foreign_key: "accepted_denied_by_user_id"

and then you will be able to get the info as:

message.denied_user.email

you shouldn't give two (or more) associations the same name.

when you do belongs_to :user it automatically looks for the User model. but when you want to associate it again - just give it some other name, and then specify class_name: "User" - so its still looking in the User model, but with the foreign_key you specified.

Rails 4 - how to use "belongs_to" on the same model twice (once with using "foreign_key")?

2 Answers2