CODEWITHSUNDEEP
ruby-on-railsactiverecord
deni5n
deni5n

Reputation: 101

how to understand the relationships in the model Rails

Such as how to get data from another of the same model? http://guides.rubyonrails.org/ usually write as to establish a relationship between the models, but it is not clear in this case to get the data can consult books or online resources with examples?

Example:

class Foto <ActiveRecord :: Base
   belongs_to: action
End

class Action <ActiveRecord :: Base
   has_many: foto
end

ActiveRecord :: Schema.define (version: 20151207105829) do
   create_table "actions", force:: cascade do | t |
     t.text "name"
   end
   create_table "fotos", force:: cascade do | t |
     t.text "fname"
     t.integer "action_id"
     t.text "image"
   end
end

how to get the following SQL

SELECT * FROM fotos
  INNER JOIN actions ON fotos.action_id = actions.id

Upvotes: 1

Views: 36

Answers (3)

CR4F7Y
CR4F7Y

Reputation: 26

Rich Peck has completely right answer. But he should add that you can get all off the photos by using @action.fotos after you will create some of them.

I.e. @action.fotos will store all of your fotos which are belonging to some @action and will correspond to 

SELECT * FROM fotos
INNER JOIN actions ON fotos.action_id = actions.id

Upvotes: 0

Richard Peck
Richard Peck

Reputation: 76774

This is a standard belongs_to/has_many relationship -- you're looking to associate two models through a database reference.

--

You've already done the hard work - you have the relevant foreign_key in your database (action_id), which means you'll be able to do the following:

#config/routes.rb
resources :actions do
   resources :fotos, only: [:new, :create]
end

#app/controllers/fotos_controller.rb
class FotosController < ApplicationController
   def new
      @action = Action.find params[:action_id]
      @foto = @action.fotos.new
   end

   def create
      @action = Action.find params[:action_id]
      @foto = @action.fotos.new foto_params
   end

   private

   def foto_params
      params.require(:foto).permit(:fname, :image)
   end
end

Upvotes: 1

Sudipta Mondal
Sudipta Mondal

Reputation: 2572

The below ActiveRecord statement should give you the fotos for a particular action

Action.find(name: "pass the name here").fotos

or if you wan to traverse in the opposite relation

Foto.find(fname: "pass the fname here").action

Note Your relationship is important, because you will need to pluralize the name of classes to fetch them accordingly.

Upvotes: 0

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