// this returns an instance variable. but the whole point of active record is to manipulate records in the database.

 for database schema update, and keeping its version control and roll backs. DB knows which version of migration it has applied so far and it is idempotent to as many times you want to call it, it knows to only do it once.

$ rails generate migration CreateMovies

app/models/movie.rb

$ rails db:migrate   

$ rake db:test:prepare    

R

find by id:

dynamic attribute-based finders:

U

D

Suppose we’ve done
movie = Movie.where("title='Amelie'")
Then another app changes the movie’s title in the database table directly. Just after that instant, the value of movie:

routes.rb :    the default setup essentially gives you the routes for all of the 'CRUD actions' on your models. You also need to add the actual code that does the thing

You've probably already added the code in the model that does the actual work. All you need to do now is basically connect that to the rest your app.

make sure there is something for it to render

one action can have multiple views associated with it

To add a new action to a Rails app
1. Create route in config/routes.rb if needed
2. Add the action (method) in the appropriate app/controllers/*_controller.rb
3. Ensure there is something for the action to render in app/views/model/action.html.haml

http://railscasts.com/episodes/217-multistep-forms
http://railscasts.com/episodes/346-wizard-forms-with-wicked
http://stackoverflow.com/questions/3619551/what-is-the-best-way-to-structure-a-multi-page-form-to-create-and-edit-models-in?lq=1

$ cd ~/Documents
$ mkdir temp
$ rails new myrottenpotatoes -t   # to avoid generating default test directories as we want to use rspec.

if you go to http://localhost:3000/movies it says undefined route

$rake routes   # shows no route
modify config/routes.rb
  resource :movies
  root :to => redirect(‘/movies’)

$rake routes   # shows routes for movie

if you go to http://localhost:3000/movies now it says undefined controller

#####create controllers/movie_controller.rb
$ rails generate migration create_movies
    this creates    db/migrate/20140307141649_create_movies.rb
There add details of a movie
   def up
    create_table 'movies' do |t|
    t.string 'title'
    t.string 'rating'
    t.text 'description'
    t.datetime 'release_date'
    t.timestamps
    end
  end

  def down
    drop_tables 'movies'
  end

$ rake db:migrate

create models/movie.rb       #all model names should be singular
  class Movie < ActiveRecord::Base

  end


combination of the migration file  and this model file tells ruby that we have a model with that schema.
Now you can directly contact the model via rails console without any code.
$ rails console
> starWars = Movie.create!(:title => 'Star Wars Morty', :release_date => '25-4-1997', :rating => 'PG')
>Movie.all         #returns all movies

create controllers/movie_controller.rb
  class MoviesController < ApplicationController

  end


if you go to http://localhost:3000/movies  The action 'index' could not be found for MoviesController
class MoviesController < ApplicationController
  def index
    @movies =  Movie.all
  end
end
if you go to http://localhost:3000/movies template missing

create views/movies/index.html.haml       same name as the action the controller is performing

it is good to have a description in the first line of haml file
-# this file is /views/movies/index.html.haml

hi

%h2

%table#movies
  %thead
    %tr
      %th Movie Title
      %th Rating
      %th Release Date
      %th More Info
  %tbody
    - @movies.each do |m|
      %td= m.title
      %td= m.rating
      %td= m.release_date
      %td= link_to "Read more about #{m.title}", movie_path(m)

     
Summary
1. routes.rb
2. create migration  for database creation
3. create empty model file
4. we used console to create a movie
4. create controller
5. create index action
5. create viewer for the action of the controller

Create equivalent haml file instead of application.html.erb : application.html.haml
!!! 5
%html
  %head
    %title My Rotten Potato Stepped Through :)

Now let’s do the show action for movie, which shows details of one movie
add the show action to movies_controller.rb
  def show
    id = params[:id]    # e.g. 1 is the id of the movie will be here  movies/1
    @movie = Movie.find(id)
  end

to show the ‘title’ of the movie as its URL, we use find_by_title instead:

———————
the form to create movie has destination URL of movies_path because if you do $rake routes you see that /movies is the path for create action.
= form_tag movies_path          which URI is gonna receive the POST method when user clicks the submit button. the target of the form submission is movies_path
movies_path combined with http post verb, will post a form to the create action of the movies controller.
the label helper will take an active record object type and one of the attributes of that object and generate a useful label.

if you are unsure go to http://api.rubyonrails.org/ and search for a method e.g. label. and in this case find label helper method.

summary

1. the form_tag specifies the controller action that will receive the form posting.

2. the helpers work with ActiveRecord models to produce human friendly markup

3. there are special created markups for things like dates, and pop-up menus

4. set flash message in create action and show it in the application.html.haml

debugger                         sets a debugger

$ rails s --debugger

n                         next line

c                          continue

edit

= button_to "Delete", movie_path(m), :method => :delete, data: { confirm: "Are you sure?" }       #generates the following self-contained form with a single submit button that calls delete action.

<form method="post" action="/movies/9"  class="button_to">
  <div>
    <input name="_method" type="hidden" value="delete" />
    <input data-confirm="Are you sure?" type="submit" value="Delete" />
    <input name="authenticity_token" type="hidden" value="FSwfhq9TCS7xyhyHx+1ltov8j4IDnQ+UjiqEfjLRsrM=" />
  </div>
</form>