Associated in 3 table rails

Question

I have to create 3rd table having assosisted with 2nd.

1st table: Schema
2nd table: Entity 
3rd table: Fields

Relation between them is:

Schema(id) ===>  Entity
Entity(id) ===> Fields

I have created table and views till Entity but don't know how to create table for field

Fields having values as:

"clientId"
"name"
"description"
"mnemonic"
"columnType"
"display"
"fallbackId"
"conceptDisplay"
"businessName"

Help me to create model and views for it to show all the fiels related to entity:

I tried something like this:

entity.rb => model

class Entity < ApplicationRecord
  belongs_to :schema
  has_many :fields, dependent: :destroy
end

field.rb => model

class Field < ApplicationRecord
  belongs_to :entity
end

schema.rb => model

class Schema < ApplicationRecord
  has_many :entities, dependent: :destroy
   has_many :fields, through: :entities

  validates :name, presence: true, uniqueness: true
  validates :schemaId, presence: true, uniqueness: true
end

controller for field:

class FieldsController < ApplicationController
  def index
    @field = Schema.find_by(id: params[:id]).fields
  end
end

views for entity where i have to create link_to to show all field for that entity

<div class="content">
  <ul>
  <% @entities.each do |data| %>
    <li>
      <%= data.clientId %>
      <%= link_to data.name, fields_index_path(id: data.id) %>
      <%= data.description %>
      <%= data.mnemonic %>
    </li>

  <% end %>
</ul>
</div>

Answer 1

You need to create these migrations:

  def change
    create_table :schemas do |t|
      # here all your necessary fields for schema
      t.timestamps
    end
  end

  def change
    create_table :entities do |t|
      t.references :schema, null: false, foreign_key: true
      # here all your necessary fields for entity
      t.timestamps
    end
  end

def change
  create_table :fields do |t|
    t.references :entity, null: false, foreign_key: true
    # here all your necessary fields for field
    t.timestamps
  end
end

And add all necessary associations to your models

# schema.rb
class Schema < ApplicationRecord
  has_many :entities
  has_many :fields, through: :entities
end

# entiry.rb
class Entity < ApplicationRecord
  belongs_to :schema
  has_many :fields
end

# field.rb
class Field < ApplicationRecord
  belongs_to :entiry
end

Fetch all fields for Schema through Entity in yout controller

# fields_controller.rb
class FieldsController < ApplicationController
  def index
    @fields = Schema.find_by(id: params[:id]).fields
  end
end

And render all links to your fields in view

# views/fields/index.html.erb
<% @fields.each do |field| %>
  <%= link_to field.name, field_path(field) %>
<% end %>

And add necessary resources to your routes

# configs/routes
resources :schemas
resources :fields