RoR Blog

應用rails搭建Blog的練習專案，旨在練習Routes及CRUD等相關操作，計劃在未來一週內繼續加上styling和更複雜的資料庫操作，並部署至Heroku讓整個專案更為完整。

to start the server on cloud9

• rails server -b $ip[ -p $port]

1. create articles table

• naming convention
  • snake-case for file names
  • camelCase for Model and Controller Name
• step 1.1. generate a migration for creating articles table
  • rails generate migration ... # migration operation matters
    • create_$tables
    • ...
    • etc.
    • 在migration file中至少會有change action/method
  • rails generate migration create_articles
• step 1.2. run the migration file to truly create the table
  • rails db:migrate
    • verify the "table schema" has been generated in $app/db/schema.rb
• others
  • want to update schema after the migration file has been executed / when you make a mistake
    • option 1. rials db:rollback for backing to empty schema
    • option 2. (recommanded) create a new migration file when make a mistake, i.e. rails generate migration add_description_to_articles
      • use add_column(tableName, columnName, valueType) function
        • i.e. add_column :articles, :description, :text
  • 記得在table加上timestamp columnsssss，且欄位名稱必須和規定相同，rails app才能夠正確的追蹤
    • i.e.
      • add_column :articles, :created_at, :datetime
      • add_column :articles, :updated_at, :datetime
  • migration file 只會被run 1 次，執行過就不會再重複執行

2. create the model ($projectName/app/models/article.rb) to communicate with the tables

• remember to follow the naming convention
• 在model建立的當下，rails會 "自動生成" 該model所對應的table的欄位的setters/getters
  • can test it through rails console
    • test the connection: Article.all
    • Article (this means the Article Model) to check the schema of the table (articles)
    • i.e.
      • article = Article.new(...)
        • 或可用資料欄位setter/getter的方式來替代操作, i.e. article.description = '....'
        • 或Article.create(...) # $Model.create(...) 會直接hit the database，不用另外操作save
      • article.save # 最後需要做save所以有的操作才會真正的去hit the database
        • begin the transaction
        • generate the sql query
        • commit the transaction
      • Article.all to check the data row has been inserted

3. edit and delete a data row

• into rails console
  • edit
    • through setter/getter
      • article = Article.find($id) # $Model.find($id)
      • article.description = '....'
  • delete
    • article.destroy # it will return the data row/ model instance that was been deleted
    • Article.all to check/verify that the data have been deleted

4. about the validation

• maintain data integrity by adding the validation to the model
  • to avoid the article like this: (title: nil, description: nil....)
• 在model中加上欄位的constraints，使能在model instance save時去做檢查，避免nil value存入

  • begin transaction

  • rollback transaction

    • to find out that why rollback
      • article.errors.any? # true
      • article.errors.full_messages # ['title can't be blank]
  • !! remember to restart the console by reload!

5. demonstrates the functionalities with UI

• it needs routes、controllers and views
• lifecycle
  • 
    • @ means it's a instance variable # ???
    • view -> controller -> model
• add the route of $rootUrl/articles/new
  • add resources :articles to $project/config/routes.rb # resources :$table
    • This will add the following routes:
      • routes path HTTP verb link controller#action
      • articles index articles GET /articles articles#index
      • new article new_article GET /articles/new articles#new
      • create article POST /articles articles#create
      • edit article edit_article GET /articles/:id articles#edit
      • update article PATCH /articles/:id articles#update
      • show article article GET /articles/:id articles#show
      • delete article DELETE /articles/:id articles#destroy
    • it will auto-generate the CRUD routes for you
      • type rails routes to check the existence routes
        • 
• refresh the page and proceed after check the error (uninitialized constant ArticlesController)
• add the controller (articles_controller.rb/ArticlesController)
  • it need the "new action" # based on the url/route

        # $projectName/app/controllers/articles_controller.rb
    
        class ArticlesController < ApplicationController
            def new
            end
        end
    

• refresh the page and proceed after check the error (ArticlesController#new is missing a template for this request format and variant. ....)
• add the templates in $porject/app/views/articles folder
  • 因為是articles_controller，所以會去views/articles底下找templates/views by request
  • add $project/app/views/articles/new.html.erb # $actionName.html.erb

        # app/views/articles/new.html.erb
    
        <h1> create an article </h1>
    

  • 增加表單
    • it's model based form, rails provides some useful tools that you can use with form_helpers (check http://guides.rubyonrails.org/form_helpers.html)

          # app/views/articles/new.html.erb
      
          <h1> create an article </h1>
          
          <%= form_for @article do |f| %>
          
          <% end %>
      

• refresh the page and proceed after check the error (First argument in form cannot contain nil or be empty)
  • 不認得template中的@article => 要在controller中去初始化 # why in controller? => 思考整個render flow

        # app/controllers/articles_controller.rb
        
        class ArticlesController < ApplicationController
            def new
                @article = Article.new
            end
        end
    

  • complete the form

       # app/views/articles/new.html.erb
        
        <h1> create an article </h1>
            
        <%= form_for @article do |f| %>
            <p>
                <%= f.label :title %><br/>
                <%= f.text_field :title %>
            </p>
            
            <p>
                <%= f.label :description %><br/>
                <%= f.text_area :description %>
            </p>
            
            <p>
                <%= f.submit %> 
            </p>
            
        <% end %>
    

• refresh the page then click the button and proceed after check the error (The action 'create' could not be found for ArticlesController.)
• add the create action to articles_controller

      # app/controllers/articles_controller.rb    
      
      ...
      
          def create
              
          end
  
  

• refresh the page then click the button and proceed after check the error
  • 
• just render what you get in the controller

      # app/controllers/articles_controller.rb    
      
      ...
      
          def create
              render plain: params[:article].inspect
          end
  
  

• refresh and test it
• save the value by the controller and the action article#create

      # app/controllers/articles_controller.rb    
      
      ...
      
          def create
              # render plain: params[:article].inspect
              
              @article = Article.new(article_params)
              @article.save
          end
          
          private
              def article_params
                  params.require(:article).permit(:title, :description)
              end
  
  

• refresh the page then click the button, 不用管error，只要在rails console確認資料真的有存database就好
  • enter the values in the browser
  • Article.all
  • enter the values in the browser
  • reload!
  • Article.all
• redirect to articles_show(@article)
  • type rails routes to check the route articles#show

        # app/controllers/articles_controller.rb    
    
        ...
    
        def create
            # render plain: params[:article].inspect
            
            ....
            redirect_to article_show(@article)
        end
    
    

  • the article_show will be introduced in the next chapter