CODEWITHSUNDEEP
ruby-on-railsassociationsrails-activerecord
Dennis Hackethal
Dennis Hackethal

Reputation: 14295

Notification associations - what's the right way to do it?

I have a Rails 3.2 application with a user model. I want to add a notification mechanism that can be triggered by the following use cases:

In all cases, one user generates a notification by his behavior that the other user will receive. So, there is a sender and a recipient of notifications.

I am now pondering how to structure my associations. So far, my models looks like the following:

Notification.rb

attr_accessible :content, :read_at, :recipient_id, :sender_id

belongs_to :sender,     class: :user
belongs_to :recipient,  class: :user

User.rb

has_many :notifications, as: :recipient, dependent: :destroy, foreign_key: :recipient_id
has_many :notifications, as: :sender, dependent: :destroy, foreign_key: :sender_id

This pseudocode shall only help understand what I need - what confuses me a lot is that I refer to the user model twice inside the notification model, and that a user has many notifications in two different ways.

So, my questions are:

Thanks!

Solution

To put Shane's solution into words, this is what the models have to look like. It was really much easier than I thought. I assumed I would have to do some magic here - but Rails tricked me again with its stunning simplicity! Well, that's why I like it so much.

Thanks a lot, Shane!

Notification.rb

attr_accessible :content, :read_at, :recipient, :recipient_id, :sender, :sender_id

belongs_to :sender, class_name: "User"
belongs_to :recipient, class_name: "User"

User.rb

has_many :received_notifications, class_name: "Notification", foreign_key: "recipient_id", dependent: :destroy
has_many :sent_notifications, class_name: "Notification", foreign_key: "sender_id", dependent: :destroy

Upvotes: 1

Views: 139

Answers (1)

Shane
Shane

Reputation: 514

This is completely normal. Here is example of the same pattern used in a Redmine, a popular open source app:

https://github.com/edavis10/redmine/blob/master/app/models/workflow_rule.rb#L23-L24

As for needing a method that gets both sent and received notifications, the answer here works well for basic needs.

Rails Model has_many with multiple foreign_keys

Upvotes: 3

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