How should this model be designed?

Question

In a Rails app, I want to allow users to send messages from one to another. So, I have a User model that will have this:

has_many :messages

I was thinking that the Message model will have a from field, containing the id of the user that sent it, and a to field, containing the user id of the user that it's addressed to. What would be the best practice for the Messsage model? Should I generate it like this:

rails g model Message from:integer to:integer title:string content:text

How would I associate it to a user? Should I associate it to 2 users, since the from and to fields reference existing users? How would I represent this relationship? What kind of relationship would I write in the message model? belongs_to :user ?

I feel there should be a way of letting Rails manage the user id's for me, so that I don't have to create integer fields myself.

Just as a heads up: `send` is a metaprogramming method in Ruby, so you may want to avoid using that word if practical. — Andrew Grimm, Mar 10 '11 at 22:35
Hey Andrew! I know, but I think that in the context of exchanging messages, using `send` doesn't suggest any metaprogramming. — Geo, Mar 13 '11 at 15:47

Ashish · Accepted Answer · 2011-03-14T04:55:54.703

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User

has_many :sent_messages, :class_name => "Message", :foreign_key => 'from'
has_many :received_messages, :class_name => "Message", :foreign_key => 'to'

Message

belongs_to :sender, :class_name => 'User', :foreign_key => 'from'
belongs_to :receiver, :class_name => 'User' :foreign_key => 'to'

edited Mar 14 '11 at 04:55

answered Mar 10 '11 at 11:28

Ashish

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I would actually name the columns from_id and to_id, but this is how I would program it. – François Beausoleil Mar 10 '11 at 13:44
Yes, that is the standard way – Ashish Mar 10 '11 at 14:05
Thank you Ashish, this works very nice. Can you show me please to what kind of database calls these would translate to? I'd like to fully understand this. – Geo Mar 13 '11 at 15:46
Assuming that `sent_messages` and `received_messages` are symbols, there shouldn't be a space between the colon and the word. – Andrew Grimm Mar 13 '11 at 21:40

score 2 · Answer 2 · edited May 23 '17 at 09:58

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If you want both you should probably do something like this

has_many :sent_messages, :class_name => 'Message', :foreign_key => 'from'
has_many :received_messages, :class_name => 'Message', :foreign_key => 'to'

This is similar to this question: Rails Model has_many with multiple foreign_keys

edited May 23 '17 at 09:58

Community

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answered Mar 10 '11 at 11:26

Jarrett Meyer

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So I'd have to generate my model like I wrote in my post? – Geo Mar 10 '11 at 11:30

How should this model be designed?

2 Answers2