[RUBY] How to make a follow function in Rails

Premise

☆ Required table ・ Users table ・ Relationships table (intermediate table) ☆ Point ・ The association is different from the usual "many-to-many"

flow

1. Make a relationship model
2. Edit & execute relationship migration file
3. Write associations in the user and relationships models
4. Write the follow function method in the user model
5. Follow to seeds
6. Create and edit relationships controller
7. Number of followers / followers, follow button installed in view
8. Write the routing
9. Write the follow function in the users controller

1. Make a relationship model

Execute relationships, which are intermediate tables, using associations to create a "many-to-many" relationship between user tables. Because followers are also users. First, let's create a relationships model.

Terminal

$ rails g model Relationship follower_id:integer followed_id:integer

The columns of the relationships table

Will be.

2. Edit & execute relationship migration file

Please edit as below

db/migrate/_creation_relationships.rb

class CreateRelationships < ActiveRecord::Migration[5.2]
  def change
    create_table :relationships do |t|
      t.integer :follower_id
      t.integer :followed_id

      t.timestamps


    end
    add_index :relationships, :follower_id
    add_index :relationships, :followed_id
    add_index :relationships, [:follower_id, :followed_id], unique: true
　 #add_index :table name,Column name
  end
end

By using add_index, data can be read / acquired faster. Once this is done, reset the migration file and use seed to populate the database with the initial data.

Terminal

$ rails db:migrate:reset db:seed

3. Write associations in the user and relationships models

First of all Write the association in the relationships model.

models/user.rb

#Take out the people you follow
has_many :active_relationships, foreign_key: "follower_id",
                                class_name: "Relationship",
                                dependent: :destroy

class_name: You can specify the Relationship class directly by using "Relationship"

models/relationship.rb

class Relationship < ApplicationRecord

 belongs_to :follower, class_name: "User"
 belongs_to :followed, class_name: "User"

 validates :follower_id, presence: true
 validates :followed__id, presence: true
end

** class_name: By supplementary setting with'User' **, it is prevented to refer to the non-existing class called follower/followed class, and it is clearly stated that it is a User class. In short, it means "belongs_to to the user model because there is no follower/followed model!".

models/user.rb

has_many :active_relationships, foreign_key: "follower_id",
                                class_name: "Relationship",
                                dependent: :destroy

#
has_many :followed_users, through: :active_relationships, source: :followed

4. Write the follow function method in the user model

5. Follow to seeds

6. Create and edit relationships controller

7. Number of followers / followers, follow button installed in view

8. Write the routing

9. Write the follow function in the users controller