NOTES

to create rails app

rails new <appName>

MVC pattern of a rails

• Modal -> Database -> validation , query, Modification of data.
• View -> HTML and ERB files / JSON / XML files -> output of application
• Controller -> Handles the request and decides how things are build.

Files and Folders

1. .ruby-version : decides the ruby version
2. config.ru : file for rack, rack -> web framework for ruby. lightweight http processor.
3. Gemfile: Gems and dependeincies
4. Rakefile : Define the commands which does the task eg. db migrate , rails new ...
5. app/assets : Images and stylesheet.
6. app/channel: ActionCabel Websockets.
7. app/controller : Decides what to do when request comes in.
8. app/helpers : some side function
9. app/javascript : javascript content goes here.
10. app/jobs: background jobs eg. upload
11. app/mailers: sending emails
12. app/models: for database communication and schema of database.
13. view: HTML and other templates goes here.
14. bin : it has excutable files
15. config/application.rb : we can difine the environments here. eg. dev, prod, test
16. config/cabel.yml : configurings websockets,
17. config/master.key : environment variables and secret keys
18. config/database.yml : connection qith database.
19. config/environment.rb : checks the enviroment of application and goes to config/enviroment folder and excute as per requirement.
20. config/puma.rb: rails server configuration
21. config/routes.rb: defined the route of applications.
22. config/storage.yml : define where we can upload the file
23. db: this will have migration details
24. db/seeds.rb : file used to add some pre-populate some data
25. lib : some assets, or some rake rask we can create
26. public: error pages, logos, static files
27. storage: file upload and other upload detaisl
28. test: test cases and automated test case.
29. tmp : stores cache data and temporary data
30. vendor: eg. if need jQuery, we can put it here.

Generators

rails g model <ModelName> fieldName:datatype fieldname:datatype 

Migration

To migrate table created on rails in to database rails db:migrate

Rails console

rails console : this will open the IRB console where we can update the database.

examples:

Some commands to update and get data in IRB

To get all blog_posts
    - BlogPost.all  

create a blogpost with give data
    - BlogPost.create(title: "Hello" , body: "the body") 

delete blogPost with id 1 
    - BlogPost.delete(1)  

find blogPost with id 2 
    - BlogPost.find(2)  

To update the blogPost : 
    - blgpst = BlogPost.find(2)
    - blgpst.update(title: "this is updated ")
    - blgpst.save

To delete it from database 
    - blgpst.destroy

Rails routes

• root route -> by default it points to /
• rails route are always defined in specific order
• syntax for route:

  controller_name#action_name 
  

• Can create different routes for GET, POST, PATCH, PUT and DELETE requests

  get '/blog_posts/:id', to: 'blog_post#show' 
  

• Grabing the params from route

      @blog_posts = BlogPost.find(params[:id])
  

• Route generator

      get '/blog_posts/:id', to: 'blog_post#show' , as: :blog_post
  

  and this will generate follwoing function in code

      blog_post_path(1) -> '/blog_posts/1'
      blog_post_url(1) -> 'http://localhost:3000/blog_posts/1'
  

NOTE: everytime we create a file in rails we make sure to create a class in that file which matches the name of that file

Controller

• Controllers are inherited from ApplicationController, and it is inherrited from ActionController::Base
• It gives a all the procesing thing to us which we can do with HTTP methods.
• Naming conventions and declaration of controller class : eg. class BlogPostsController
• File Nomenclature: eg. `

Views

• every view is associated with controller. So, in view also we need to create /blog_posts/index.html.erb file
• Instanct Varible are gloab variable that are declared in controller and can be accessed in a view.

  @blog_posts = BlogPost.all
  

• ERB tags

  <% 1 %>  -> // is not visible in html 
  <%= 2 %> -> // will be visible to html
  

Rescue method

• Record not found:

    rescue ActiveRecord::RecordNotFound
        redirect_to root_path
    end
    // root_path -> "/"

link_to helper

<%= link_to <text we want to disply> ,'<route we want it to redirect>' %> eg.

    <%= link_to @blog_title ,'/blog_posts/#{@blog_title.id}' %> 

htmls rails forms

we need to route to be added in the form

1. POST REQUEST - post "/blog_posts" , to: "blog_posts#create", as: :blog_posts
2. GET REQUEST - get "/blog_posts/new", to: "blog_posts#new", as: :new_blog_post

We also need to add functions in controller to work this. And form code can be seen like below.

<%= form_with model: @blog do |form| %>
    <div>
        <%= form.label :title %>
        <%= form.text_field :title %>
    </div>
    <div>
        <%= form.label :body %>
        <%= form.text_area :body %>
    </div>
    <%= form.button %>
<% end %>

new function ins controller

    def new
        @blog = BlogPost.new
    end

allowing params to the controller

• it is private method
• params.require(<Parameter>).permit(<list of allowed fields>)

      private
    def blog_post_allowed_params
        params.require(:blog_post).permit(:title, :body)
    end

Helper before_action

• This action run before running of any function before_action :[Symbol], only: [Array of action names], except: [Array of actions]

   before_action :set_blog_post_by_id, only: [:show, :delete, :update, :edit] , except: [:new]

Gem: Devise

• bundle install devise

• rails g devise:install

• rails g devise User

• rails db:migrate

• devise generate the view and route along with controller, which we can use directly

• before_action method is alos provided by device which we can call for authorization.

• before_action :authenticate_user!

Rails migration

• Add<NameOfColumn>To<NameOfTable> <column_name>:<format>

rails generate migration AddPublishAtToBlogPosts published_at:datetime