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Part 3 of 6
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Building Web Apps with Rails
III
● Rails Console● ActiveRecord Queries
● Views● Embedded Ruby Syntax● Layouts● Helper Methods
Recap
Recap: ActiveRecord
DBModels Controllers
In stations_controller.rb (show):
@stations = Station.find(params[:id])
The Rails Console
1. Open the terminal 2. Navigate to the 'firstfm' directory3. Run the commands:
rails console@stations = Station.all
<%= link_to 'Edit', edit_station_path(@station) %> |<%= link_to 'Back', stations_path %>
show.html.erb:
These are both view helpers.
<!DOCTYPE html><html><head> <title>Firstfm</title> <%= stylesheet_link_tag "application" %> <%= javascript_include_tag "application" %> <%= csrf_meta_tags %></head><body>
<%= yield %>
</body></html>
The default layouttemplate.
DB
Web Browser
Models
Routing SystemRails
Controllers
Views
Session 3
DB
Web Browser
Models
Routing SystemRails
Controllers
Views
Session 3: Routing
DB
Web Browser
Models
Routing SystemRails
Controllers
Views
Session 3: Validations & Testing
DB
Web Browser
Models
Routing SystemRails
Controllers
Views
Session 3: Associations& The 'Stream' Model
Routing in Rails
Routing in Rails
●Which controller to instantiate
●Which action to invoke
●Parameter(s) to pass
Web Browser
?
Routing in Rails
●Follows routing rules defined in:
●config/routes.rb
Web Browser
Routing System
Controllers
Views
Config/Routes.rb:
Firstfm::Application.routes.draw do resources :stations #commentsend
Routing in Rails
Generates RESTful routes for the 'Station' resource
Config/Routes.rb:
Firstfm::Application.routes.draw do resources :stations #commentsend
Routing in Rails
Representational State Transfer Principles:
Use HTTP methods explicitlyBe stateless
Expose directory structure-like URIsHandle multiple formats e.g. XML, JSON
Config/Routes.rb:
Firstfm::Application.routes.draw do resources :stations #commentsend
Routing in Rails
This means we can acceptrequests for all the CRUD
actions
Routing in Rails: Terminal Time!
1. Open the terminal 2. Navigate to the 'firstfm' directory3. Run the commands:
rake routes
Routing in Rails: Writing Rules
Config/Routes.rb:
resources :stations
Routing in Rails: Writing Rules
Config/Routes.rb (rewritten):
get 'statations' => 'stations#index'get 'statations/:id' => 'stations#show'get 'statations/new' => 'stations#new'post 'statations' => 'stations#create'put 'statations/:id' => 'stations#update'delete 'statations/:id' => 'stations#destroy'
Routing in Rails: Writing Rules
Config/Routes.rb:
resources :stations
Generates URL helpers for us e.g.
stations_pathstation_path(:id)new_station_pathEtc...
Routing in Rails: Task
1. Define a root controller and action
2. Add a new action
2.1 Write a new method in the controller2.2 Write a view file for it2.3 Write a routing rule so we can access it
For docs on routing: guides.rubyonrails.org/routing.html
Tests and Validations
We have a problem...
Our app accepts empty station data
Solution:
Write validations to prevent erroneous data
Tests and Validations
But First!
Let's write tests.
Tests and Validations
Tests and Validations
Scaffolding has generated testfiles for us
require 'test_helper'
class StationTest < ActiveSupport::TestCase # test "the truth" do # assert true # endend
In firstfm/test/unit/station_test.rb:
We write tests by writing out 'assertions'
Tests and Validations: Unit Testing
require 'test_helper'
class StationTest < ActiveSupport::TestCase test "the truth" do assert 10 > 9 endend
Tests and Validations: Unit Testing
'assertions' evaluate whether an object is what we expect it to be
Tests and Validations: Unit Testing
ruby -Itest <script_name>
Running test scripts
ruby -Itest test/unit/station_test.rb
e.g.
Tests and Validations: Unit Testing
Script report example:
ruby -Itest test/unit/station_test.rb
pass: 1, fail: 1, error: 0total: 2 tests with 2 assertions in 0.215168805 seconds
test "shouldnt save without name" dostation = Station.newstation.url = “http://myradio.com”station.description = “A cool radio
station”assert !station.save
end
Tests and Validations: Unit Testing
test "should save" dostation = Station.newStation.name = “My Radio”station.url = “http://myradio.com”station.description = “A cool radio
station”assert station.save
end
Tests and Validations: Unit Testing
Tests and Validations: Task!
Write test cases for your validations
Consider more than just presence of data e.g.
● Name shouldn't be longer than x characters
● URL should start with 'http://'
● Description shouldn't be less than x characters
Tests and Validations: Validate
● We write validation code in the model
● Rails provides us with several built in validation methods
● For example: 'validates_presence_of'
Tests and Validations: Validate
Example: Using validates_presence_of In models/station.rb:
class Station < ActiveRecord::Base
validates_presence_of :name, :url, :description
end
Tests and Validations: Task!
Make your tests pass by implementing validations like below
class Station < ActiveRecord::Base
validates_presence_of :name, :url, :description
end
Associations in RoRAdding 'Streams'
Station
First FM
Station Stream
First FM
Station Streams
First FM
Has many
First FM
Let's generate the stream model
rails generate model stream url:string name:string
Create the db table by running the migration script...
rake db:migrate
First FM
Let's check out our new stream model
rails c
mystream = Stream.new
Station Stream
First FM
Station Streams
First FM
Has many
Station Streams
First FM
Has many
has_many :streams
belongs_to :station
First FM
Let's see if our models are associated
rails c
mystation = Station.first
mystation.streams
First FM
OH NOES!
We need to add a secondary key.
rails generate migration AddStationIdToStreams station_id:integer
First FM
OH YEA!
We've got a secondary key!
rake db:migrate
rails c
mystation = Station.first
mystation.streams
First FM
Build
Build and save a new stream
stream = mystation.streams.build
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