Rails Controllers and Views: Understanding Control Structures and Templates
"Learn about control structures, templates, and the use of controllers in Rails development. Explore examples of displaying prime numbers and working with parameters in this comprehensive guide."
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Simple Rails Template <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>Hello, User</title> </head> <body> <p> This page was fetched at <%= Time.now() %> </p> </body> </html> CS 142 Lecture Notes: Rails Controllers and Views Slide 1
Control Structures in Templates ?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>Rails Parameters</title> </head> <body> <p> The <code>params</code> hash contains the following values: </p> <% params.each do |key, value| %> <p><%= key %>: <%= value %></p> <% end %> </body> </html> CS 142 Lecture Notes: Rails Controllers and Views Slide 2
Control Structures, contd Template: ... <% params.each do |key, value| %> <p><%= key %>: <%= value %></p> <% end %> ... HTML: ... <p>x: 44</p> <p>y: 92</p> <p>action: showParams</p> <p>controller: rails_intro</p> ... CS 142 Lecture Notes: Rails Controllers and Views Slide 3
Controller: Compute Primes class RailsIntroController < ApplicationController def show_primes if params[:count] != nil then count = params[:count].to_i() else count = 10 end Query value determines # primes to compute Fill in @primes array with prime numbers @primes = [] candidate = 2 while @primes.length < count is_prime = true @primes.each do |prime| if (candidate % prime) == 0 then is_prime = false break end end if is_prime then @primes << candidate end candidate += 1 end end end CS 142 Lecture Notes: Rails Controllers and Views Slide 4
Template to Display Primes <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE ...> <html ...> <head> <title><%= @primes.length %> Prime Numbers</title> <%= stylesheet_link_tag 'main' %> </head> <body> <p> The first <%= @primes.length %> prime numbers are: </p> <table class="oddEven" cellspacing="0"> <tr class="header"><td>Prime Numbers</td></tr> <% @primes.each do |prime| %> <tr class="<%= cycle('odd', 'even') %>"> <td><%= prime %></td> </tr> <% end %> </table> </body> </html> CS 142 Lecture Notes: Rails Controllers and Views Slide 5
Directory Structure app controllers rails_intro_controller.rb student_controller.rb views rails_intro hello.html.erb show_params.html.erb show_primes.html.erb student models assets images javascripts stylesheets main.css db migrate CS 142 Lecture Notes: Rails Controllers and Views Slide 6
Layouts app/views/layouts/application.html.erb: <?xml version="1.0" encoding="utf-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title><%= @title %></title> </head> <body> <%= yield %> </body> </html> app/views/rails_intro/hello.html.erb: <% @title = "Hello, user" %> <p> This page was fetched at <%= Time.now() %> </p> CS 142 Lecture Notes: Rails Controllers and Views Slide 7
