T-13 to Course Start

Ruby Tutorial – end of 5,

  • Setting up our Links
    • Testing for routes: convert things like: visit '/static_pages/help' to visit help_path
      • eliminate duplication with the before { stuff to do } statement at the beginning of a describe block
      • if your specs are written so well that descriptions are redundant, and that many it blocks examine the same method or element, you can begin a block with the subject { victim_variable_or_method_here } statement, and then put each should statement in the curly braces – this is thanks to the help of Capybara
      • Rspec will also automatically look in the spec/support directory, so adding in ruby files there with useful methods and referencing them from files in the spec/requests/ directory works fine… i.e. the name of the file is not important
        • you can safely include the name of a module that appears elsewhere, like in app/helpers/ , if it is required for the methods being run in the spec
    • Checking that links go to the correct place (rather than just testing the routing with visit)
      • click_link to load a page, and then run some identification test on that page
  • Reducing redundancy with shared examples
    • using a shared_examples_for "template name" block, you can template tests, using some variables in the template, which are then called with it_should_behave_like "template name" , for which variables are instantiated before the call with: let(:variable1) { 'text that variable represents' }
  • Defining routes: in the config/routes.rb file, converting things like get "static_pages/home" to match '/help' , to: 'static_pages#help'
    • arranges for a valid page at /help
    • and a named route called help_path
    • match is interchangable with get here, but it is more conventional as is
    • the to: signifies that all matches of about will be routed to the StaticPages controller
      • about_path => '/about' is created
      • about_url => 'http://localhost:3000/about' is created
  • A new controller
    •  rails generate controller Users new --no-test-framework
      • generates a Users controller with a new action
      • --no-test-framework because we are using RSpec
        • right after, we do: rails generate integration_test user_pages
      • familiar match statements fo into the routes.rb file, but a get 'users/new' is still required
  • Data in Rails
    • model = default data structure
      • using attar_accessor within a model ensures that only the variables specified are made available to users
    • Migrations – a feature to allow data definitions to be written in Ruby, and no SQL data definition language
      • incrementally alter database
      • change method, change that will be made to the database
      • Case
        • table name is plural
        • singular for model
        • plural for controller
      • db:migrate is “migrating up”
      • db:rollback is “migrating down”
      • for tests to work, the test database needs to be updated too: bundle exec rake db:test:prepare
  • The Annotate gem
    • adds comments containing the data model to the model file! nice visualization!
  • rails console --sandbox results in all changes being rolled back when the console is quit
  • RSpec boolean convention – Ruby boolean values can be used in RSpec if the question marks are dropped off

Rails for Zombies 2 – Level 1

  • Level 1
    • Bundler
      • installs dependencies as specified by Gemfile
      • configuration in config/database.yml
    • rails g scaffold zombie name:string (has the format: column_name:type)
      • availible types: string, text, integer, boolean, decimal, float, binary, date, time, datetime
    • Migrations (Rails Guide) – keeping track of changes
      • in db/migrate/ contains a primary key called id; represented by the |t| (t for table)
        • creates a table, via create_table, with certain fields as specified in the scaffold command
        • makes a t.timestamps, creating and updating a datetime
        • to update the table manually: add_column :table_name, :field, :type, option_name: option
          • instead of add_column, can also do additional commands: rename_column, rename_table, drop_table, change_column, change_column_defaut, remove_column
            • for Example: rename_column takes 3 args, name of table, name of column to rename, new name of column
        • to update the table via commandline:
            • rails g migration AddEmailAndRottingToZombies email:string rotting:boolean
            • adds two columns to our database
            • adding column options: default, limit, (cant be) null, positio, unique
          • still need to run rake db:migrate
    • need to run a migration to include something in the database
      • rake db:migrate
    • rake db:rollback undoes at the database level
    • rake db:shema:dump (dumps current db state)
      • run by default when you db:migrate
      • will show db/schema.rb which contains current db contents
      • related to: rake db:setup which creates the db, loads schema and runs seed data
        • this is what should be run after you implement someone’s old, heavily used db, to get the last state
    • removing something from the database
      • rails g migration RemoveAgeFromZombies age:integer
      • separate up and down methods for migrating forward and backward
  • Level 2
    • Named scope – returning particular items in the db
      • scope :name, method_on_db(args) under models (where it is a method used often), will allow a method called name to be called on the db in the controller: Table.name
      • scope :recent, order("created_at desc").limit(4)
      • works fine with chaining
    • Callbacks
      • Put logic, like conditional statements and actions that are reused, into a model
        • model methods: using self, not instance variables
      • then call this logic with key phrases like: before_save :method1, or after_update, or before_destroy
      • careful of return values, model will halt at false
    • Relationships
      • have two tables, Zombie  and Brain , linked together with belongs_to and has_one , to make sure that when one is destroyed the other linked table entry is too, do dependent: :destroy right after the relationship that points to the model that you want to effect
        • similar options: foreign_key:, primary_key:, validate: true (check two table’s validation rules before saving)
      • N+1 query – list each entry in a db with an attribute’s value (one entry loading after another in series)
        • instead, Table.includes(:attribute).all will be much more efficient (in some controller method)
      • has_many: through
        • when you need to have multiple roles/attributes for one category for an item in a table – belongs_to only works with one value for an attribute
        • Instead, have an  intermediate table, where the  first and third table both has_many Assignments, and assignments belongs_to both first and third, and then first has_many thirds, through: :intermediate, and vice versa
        • singular tense with belongs_to!
        • can then add multiple third attributes to first, or one, like appending an array onto the owner
          • z.roles << Role.find_by_title("Captain")
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