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Introduction to Rails

Core concepts:

  • Routes
  • Controller actions
  • Rails uses the REST architecture style for organizing our controllers
    • Representational State Transfer (ReST)
    • Provides a standard for specifing resources over HTTP in a predictable way
    • Standard set of URLs and verbs that perform actions on resources
    • Let's say we were managing data for some Teams.
    • Rails will generate, if we specify resources :teams in our routes.rb a set of routes for us to perform all the CRUD actions.
    • Those routes are:
PurposeVerbURLActionPath helperTemplate name
Showing list of teamsGET/teamsindexteams_path or teams_urlviews/teams/index.erb
Showing HTML form for creating a new teamGET/teams/newnewnew_team_path or new_team_urlviews/teams/new.erb
Creating a new teamPOST/teamscreateteam_path or team_urlnone, code redirects
Show a specific teamGET/teams/:idshowteam_path(team) or teams_url(team)views/teams/show.erb
Show an edit page for a teamGET/teams/:id/editeditedit_team_path(team) or edit_team_path(team)views/teams/edit.erb
Update a specific teamPUT/teams/:idupdateteam_path(team) or teams_url(team)none, code redirects
Delete a specific teamDELETE/teams/:iddestroyteam_path(team) or teams_url(team)none, code redirects
  • Forms

    • Leverage many rails helpers.
    • form_for(@team) knows if this is creating a team, or updating a team.
      • How does it know? There is a persisted? method that tells us if this is saved or not
  • HAML

    • Alternative to ERB, achieves the same goal (generating HTML) but reduces syntax overhead
    • Core Principles
      • Markup Should be Beautiful
      • Markup Should be DRY
      • Markup Should be Well-Indented
      • HTML Structure Should be Clear
    • HIGHLY indentation dependent, indentation is everything in HAML as it determines when tags end.
    • Also see slim if haml is too much syntax for you. :grin:
    • Documentation
  • Authentication

    • see

API mode apps

How to start a new rails app

  • When we run rails new it will create a folder for our project, so before running it, cd to a directory you want to be the PARENT directory.
    • e.g. cd ~/sdg/week-9/day-1
  • Then create your rails app
    • rails new --skip-spring --database postgresql --api amazingapp
      • --skip-spring turns off a feature that attempts to make the app start faster, but often causes us problems, so we'll skip it in the beginning
      • --database postgresql says to use our postgress database as the default (normally sqlite)
      • --api says we are making an API only app (no HTML views)
  • rails new created a directory amazingapp so we have to change directory to it
    • cd amazingapp
  • First thing we do when creating a rails app, cloning it, or pulling down code (maybe from a coworker or co-student) is update our gems:
    • bundle
  • Since this a new app we will create the databases
    • rails db:create
  • We will be using the jbuilder library for generating json so uncomment it in the Gemfile and run bundle install
  • Now we can start coding!

Creating scaffolds

  • Identify the model you want to create
    • What is the real-world or abstract thing you are trying to manage the data for?
    • e.g. is it sports teams, or employees, or if it was an app for managing a theater, it is shows
    • Once you have identified the thing we are modeling, identify all of the attributes you want to track
      • For instance, for Teams
        • name
        • description
        • sport
        • mascot
      • For employees
        • name
        • start_date
        • department
        • salary
      • For shows
        • title
        • genre
        • performance_date
  • When you have all the attributes you can use a rails generator to create the model, the migration, the controller. If this wasn't an API mode app, it would also create the views
    • scaffold generate a generic template for each of these.
    • Usually these need to be modified (specifically the views) to fit your needs.
    • Each of these could be created manually, or with other generators.
  • Command examples:
    • rails generate scaffold team name:string description:string sport:string mascot:string
    • rails generate scaffold employee name:string start_date:date department:string salary:integer
    • rails generate scaffold show title:string genre:string performance_date:date
  • What gets generated:
    • In db/migration a file with a timestamp and a name will be created
      • This migration describes how to create the table
    • In app/models a file will be created to hold the ActiveRecord model
    • In app/views a set of views will be created. These will support index, new, edit, show
    • In app/controllers a controller file will be created that performs the correct steps to implement:
      • index
      • new
      • create
      • edit
      • update
      • show
      • destroy
    • In test go testing code for all of the above
  • Review your new migration
    • Make sure it has all the fields you want
  • Run the migration
    • rails db:migrate
    • This will create the new table representing the new model
  • Run the application

Rails and CORS

  • Uncomment rack-cors to the Gemfile and run bundle install

  • Edit cors.rb and add the following

Rails.application.config.middleware.insert_before 0, Rack::Cors do
allow do
origins '*'
resource '*', headers: :any, methods: [:get, :post, :put, :delete, :options]

Non-API mode

Creating an app with HTML, CSS, and JS views

  • TODO

Creating static pages

  • What if you just want a static page, perhaps a landing page, or an about page?
  • We need at least the controller and view parts (and maybe a model if we have some data to show)
  • We can generate a controller with some actions (and views) with another generator command:
    • rails generate controller Pages home about contact faq support
    • This will create a PagesController with actions forhome,about,contact,faq, andsupport`
    • It will also create the view files for these as well
    • It will also create entries in routes.rb to provide us paths to these actions and corresponding path/url helpers
  • How do we use these?
    • We could link to the pages like this:
      • link_to "All About Us", pages_about_path
      • link_to "Frequently Asked Questions about our product", pages_faq_path
      • etc.
    • What about setting the home page?
      • in config/routes.rb we can specify what controller and action Rails should use when visiting the root (e.g. /) of our app
      • root "pages#home"
      • The format within the string here is the downcased, plural, short name of the controller, followed by # and then the name of the action.
      • Now when we visit our app's root URI, we will be shown the home page of our app.
      • Typically you will style this as a landing page, or perhaps, in the case of a site like reddit or hacker news you just show a content page

Customizing views

  • The views the default Rails generators create are not very user friendly
  • I have setup your environments to use a bootstrap style set of generators to give a nicer default template
  • This still needs to be customized based on the application you are creating.
  • Bootstrap does not remove the need to apply styling to your application!
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