Rails column association with integer array

Question

I have 2 models, User and Email, As it's clear a user will have an email, as sender and recipient.

In User model

  has_many :sent_emails, class_name: "Email", foreign_key: "sender_id"
  has_many :received_emails, class_name: "Email", foreign_key: "recipient_id"

and in Email model

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

That's how am getting associations, That's was for information only, The problem is: I have other 2 columns as cc and bcc as

add_column :emails, :cc, :integer, default: [], array: true
add_column :emails, :bcc, :integer, default: [], array: true

I want to make associations between email and user on those columns as well.

So That if I add,

 => #<Email id: nil, sender_id: 5, recipient_id: 10, body: "Hello its first email.", subject: "Hello Hello", state: 1, head: nil, tail: nil, created_at: nil, updated_at: nil, cc: [9, 8], bcc: [4,19]>

As I can do Email.first.sender or Email.first.recipient I can get the user, So that I may do Email.first.cc or Email.first.bcc I can get the users.

As I can do User.first.sent_emails and User.first.received_emails, I can get User.first.cc_mails or User.first.bcc_mails?

Is that possible to build association like that?

why not just a one to many table, but using pg array?

Leonardo Wong
– Leonardo Wong

2017-03-19 16:33:08 +00:00
Commented Mar 19, 2017 at 16:33 — Leonardo Wong
– Leonardo Wong, Commented Mar 19, 2017 at 16:33
How? i have no idea how to do that?

Junaid Farooq
– Junaid Farooq

2017-03-19 16:45:25 +00:00
Commented Mar 19, 2017 at 16:45 — Junaid Farooq
– Junaid Farooq, Commented Mar 19, 2017 at 16:45
Actually there are going to be many CC or BCC to one email,

Junaid Farooq
– Junaid Farooq

2017-03-19 16:46:09 +00:00
Commented Mar 19, 2017 at 16:46 — Junaid Farooq
– Junaid Farooq, Commented Mar 19, 2017 at 16:46

Ilya Lavrov · Accepted Answer · 2017-03-20 11:09:04Z

1

Unfortunately Rails does not support has_many relation for this kind of structure. But you can make manual methods cc_emails and bcc_emails:

class User < ActiveRecord::Base
  ...

  def cc_mails
    Email.where("? = ANY (cc)", id)
  end

  def bcc_mails
    Email.where("? = ANY (bcc)", id)
  end
end

answered Mar 20, 2017 at 11:09

Ilya Lavrov

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Comments

azarkon · Accepted Answer · 2017-03-20 17:06:27Z

The more idiomatic rails way to build this sort of relationship to use the has_and_belongs_to_many or has_many :through association:

http://guides.rubyonrails.org/association_basics.html#the-has-and-belongs-to-many-association

This will use a pivot table instead of an integer array in the database. The documentation (linked to above) describes how to create the database schema for this.

You can then define the association on your user model something like:

has_many :ccs has_many :ccd_emails, through: :ccs

Using this schema and these associations, ActiveRecord will give you the functions you want built in, including User#ccd_emails and User#ccd_email_ids which will give you array-like representations of User instances or integers ids respectively.

This also has the advantage that it is 100% portable to different databases.

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