CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3
Vlad Khomich
Vlad Khomich

Reputation: 5880

custom rails has_many association ( through pg array )

So basically I'd like to know if there's some common approach to define own association types. Some details:

I have a model conversations that has a PG array column user_ids. So, to retrieve user conversations I need to run: select conversations.* from conversations where USER_ID = ANY(conversations.user_ids)

Since finder_sql and it's friends are deprecated now, I would really like to know what would be the best way to implement this pseudo has_many association?

currently I just use the methods like:

 def conversations
   Conversation.where("#{id} = ANY (conversations.users)")
 end

So basically I'm thinking of implementing my own ActiveRecord::Associations::CollectionAssociation and would like to know if there're some good references or if you could advice where to start at

Upvotes: 19

Views: 4959

Answers (3)

melsatar
melsatar

Reputation: 61

I suggest to normalize your model to have another table who keeps the relations between users and conversations for example, building a model like

UsersConversation

and your relations will be

class User < ApplicationRecord
  has_many :users_conversations, :dependent => :destroy
  has_many :conversations, :through => :users_conversations
end

class Conversation < ApplicationRecord
  has_many :users_conversations, :dependent => :destroy
  has_many :users, :through => :users_conversations
end

Then you can easily do

#users for each specific conversation
@users = Conversation.find(1).users
#conversations for each specific user
@conversations = User.find(1).conversations

Unless you want to keep the same way or array, you can do it like

@users = User.where(:id => Conversation.find(1).user_ids)

if the user_ids stored as array like [1,10,20] So, it will work fine and return the users

Upvotes: 2

Chung Phước
Chung Phước

Reputation: 19

You should re-structure it to the reference table where it holds the conversation_id and user_id, then you can use it the best practice from Rails (https://guides.rubyonrails.org/association_basics.html#the-has-many-through-association)

If you still want to keep this structure I suggest:

User.where(id: conversion.user_ids) (conversion is an instance of the Conversation table)

Upvotes: 1

Hamdan
Hamdan

Reputation: 193

How about:

Conversation.user.select{ |conversation| conversation.user_ids.include?(params[:id])

Considering that user_ids column is serialized and the current user id is passed by params[:id]

The main approach is that, if you have an array you can check if it have 'something' inside with .include?(something) method. Thinking this way, you can use select method to actually select the objects (users, in this case) that have its IDs inside this array with the include method. Am I being clear?

Tell me if it worked...

Upvotes: 0

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