Rails Study

Rails Philosophy

  1. DRY – “Don’t Repeat Yourself” – suggests that writing the same code over and over again is a bad thing.
  2. Convention Over Configuration – means that Rails makes assumptions about what you want to do and how you’re going to do it, rather than requiring you to specify every little thing through endless configuration files.
  3. REST is the best pattern for web applications – organizing your application around resources and standard HTTP verbs is the fastest way to go.
    • Using resource identifiers such as URLs to represent resources.
    • Transferring representations of the state of that resource between system components.

Install Rails

  1. according to steps on offical website do 
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    gem install rails; rails new rails-test; cd rails-test; rails server
  1. when running rails server i met such problem:
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    $ rails server
/home/zheng/.rvm/gems/ruby-2.0.0-p0/gems/execjs-1.4.0/lib/execjs/runtimes.rb:51:in `autodetect': Could not find a JavaScript runtime. 
See https://github.com/sstephenson/execjs for a list of available runtimes. (ExecJS::RuntimeUnavailable)

This means i need a js engine, and i install the nodejs instead, and it's ok

  1. try to open localhost:3000, and you'll see welcome page

  2. Switch to MySQL instead of SQLite3:

    • the config file is in config/database.yml and change the "development" section like that
    • add gem 'mysql2' to Gemfile
    • run rake db:create to check is there any problem 
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      development:
    adapter: mysql2
    encoding: utf8
    database: rails-test
    pool: 5
    username: root
    password:
    socket: /var/run/mysqld/mysqld.sock

Remember the test section will also be set to mySQL

Hello Rails

  1. Try to run rails generate controller home index then u will see many files created
    • create home folder and create index page
    • modify app/views/home/index.html.erb which will tell us how to show index page
    • rm default index "public/index.html" which is the static page
    • modify config/routes.rb uncomment and change to root :to => "home#index"

Creating a Resource

  1. Create by scaffold like rails generate scaffold Post name:string title:string content:text

  2. Running a Migration

    • Migrations are Ruby classes taht are designed to make it simple to create and modify database tables. it's path db/migrate/#timestamp#_create_posts.
    • run the migration:
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      $ rake db:migrate

  3. Add a Link add <%=link_to "My Blog", posts_path%> to index.html.erb

  4. Add some data, now using rails console

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    p = Post.new(:title => "Title", :content=>"Hellooo", :name=>"myself")
p.save  #if error, try to show "p.errors.full_messages"
  1. Listing All Posts
    • try to look at app/controllers/posts_controller.rb each method is resposed to each action
    • in app/views/posts/, each file corresponds to the action name, and u can modify the erb file
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      class PostsController < ApplicationController
  # GET /posts
  def index
    @posts = Post.all   # => an array of all posts
    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @posts }
    end
  end
  ...
end

6.Customize Layout, u should create erb file in layout to specific layout, like app/views/layouts/posts.html.erb, and the file application.html.erb is for whole website

Detail Study

Models

Views

Controllers