CODEWITHSUNDEEP
ruby-on-railspostgresqlrelational-database
user3882976
user3882976

Reputation: 105

Using Relational Database

I have three tables Business, Users, and Subscriptions. The goal is to be able get the business' names associated with the user. The result should be an array of business names that the user has signed up for in subscriptions

List of Tables

Schema |       Name        | Type  |
--------+-------------------+-------
 public | businesses        | table 
 public | subscriptions     | table 
 public | users             | table

Businesses Table

  Column   |            Type                                                        
------------+-----------------------------
 id         | integer                      
 name       | character varying(255)       
 created_at | timestamp without time zone  
 updated_at | timestamp without time zone

Business Model

class Business < ActiveRecord::Base

end

Subscriptions Table

   Column    |            Type                                   
-------------+-----------------------------
 id          | integer                     
 user_id     | integer                      
 business_id | integer                      
 created_at  | timestamp without time zone  
 updated_at  | timestamp without time zone

Subscription Model

class Subscription < ActiveRecord::Base
   belongs_to :user
   belongs_to :business
end

Users Table

     Column      |            Type                                   
-----------------+-----------------------------
 id              | integer                 
 username        | character varying(255)       
 password_digest | character varying(255)       
 email           | character varying(255)       
 created_at      | timestamp without time zone  
 updated_at      | timestamp without time zone

User Model

 class User < ActiveRecord::Base
       has_secure_password
       has_many :subscriptions
    end

Rails Console

 u = User.find(1)
 u.subscriptions.businesses.name

 Response: undefined method `business'

Upvotes: 1

Views: 61

Answers (2)

Jordan Running
Jordan Running

Reputation: 106037

Instead of doing an additional query for every single Subscription (as in Alireza's answer), you can do this with just one query using Rails' built-in includes method:

subscriptions = u.subscriptions.includes(:business)

This will return a relation for all of the Subscriptions including their associated Businesses. Now you can get the business' names without doing an additional query:

business_names = subscriptions.map {|sub| sub.business.name }

I think you can also do this in one step using pluck:

business_names = u.subscriptions.includes(:business).pluck("businesses.name")

I'm not certain pluck plays nice with includes, but it's worth a try.

Upvotes: 1

Alireza
Alireza

Reputation: 2691

since User has many Subscriptions, the call to u.subscriptions returns an array of Subscriptions, therefore you need to loop through the array and call the business association on each record. you can achieve what you need using:

business_names = u.subscriptions.map {|subscription| subscription.business.name }

Upvotes: 1

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