Microblog App 4 - Microposts resource 2020

Now that we've completed a quick overview of the Users resource (Microblog 3), in this chapter, we will examine microposts resource.

In this section, we'll generate scaffold code for the microposts resource using rails generate scaffold implementing the data model as shown in the table below:

microposts table:

$ rails generate scaffold Micropost content:string user_id:integer
Running via Spring preloader in process 16008
      invoke  active_record
      create    db/migrate/20160127235735_create_microposts.rb
      create    app/models/micropost.rb
      invoke    test_unit
      create      test/models/micropost_test.rb
      create      test/fixtures/microposts.yml
      invoke  resource_route
       route    resources :microposts
      invoke  scaffold_controller
      create    app/controllers/microposts_controller.rb
      invoke    erb
      create      app/views/microposts
      create      app/views/microposts/index.html.erb
      create      app/views/microposts/edit.html.erb
      create      app/views/microposts/show.html.erb
      create      app/views/microposts/new.html.erb
      create      app/views/microposts/_form.html.erb
      invoke    test_unit
      create      test/controllers/microposts_controller_test.rb
      invoke    helper
      create      app/helpers/microposts_helper.rb
      invoke      test_unit
      invoke    jbuilder
      create      app/views/microposts/index.json.jbuilder
      create      app/views/microposts/show.json.jbuilder
      invoke  assets
      invoke    coffee
      create      app/assets/javascripts/microposts.coffee
      invoke    scss
      create      app/assets/stylesheets/microposts.scss
      invoke  scss
   identical    app/assets/stylesheets/scaffolds.scss

We need to run the migration to update our database with the new data model (microposts):

$ bundle exec rake db:migrate
== 20160127235735 CreateMicroposts: migrating =================================
-- create_table(:microposts)
   -> 0.0191s
== 20160127235735 CreateMicroposts: migrated (0.0201s) ========================

The scaffold generator has updated the Rails routes file with a rule for Microposts resource:

Rails.application.routes.draw do
  resources :microposts

  resources :users

end

The resources :microposts routing rule maps micropost URLs to actions in the Microposts controller as shown in the following table:

The Microposts controller (app/controllers/microposts_controller.rb) looks like this:

class MicropostsController < ApplicationController
  before_action :set_micropost, only: [:show, :edit, :update, :destroy]

  def index
    ...
  end

  def show
    ...
  end

  def new
    ...
  end

  def edit
    ...
  end

  def create
    ...
  end

  def update
    ...
  end

  def destroy
    ...
  end
end

We enter information at the new microposts page, /microposts/new:

After creating two microposts, we can see the list:

To implement length constraint in Rails, we ca use a length validation (app/models/micropost.rb):

class Micropost < ActiveRecord::Base
  validates :content, length: { maximum: 140 }
end

We can see the validation is working from the picture below (more than 140 characters):