To Lecture Notes

IT 231 -- 10/23/12

Review Questions

1. Name some methods of the Array class.
   Ans: new, length, delete, empty?, [ ], ==
    
2. Name some methods of the Range class.
   Ans: new, begin, end, to_a, include?, ==
    
3. How to you place a literal double quote character in a Ruby String object?
   Ans: Use \" .
    
4. What is shown in the browser?
   

   <ol>
       <li>Line 1<br /></li>
       <li>Line 2<br /></li>
       <li>Line 3</li>
   </ol>
   

   Ans: The output is
    
   
   1. Line 1
   2. Line 2
   3. Line 3
   
   If you want the output to be double spaced, use this code instead
   

   <ol>
       <li>Line 1<br />&nbsp;</li>
       <li>Line 2<br />&nbsp;</li>
       <li>Line 3</li>
   </ol>
   

5. How can you change the type of numbers used in an ordered list?
     Ans: Use the following css style:
   

   ol { list-style-type: upper-roman; }
   



6. What does each of these Ruby code fragments do?

   # Problem 2a.
   (1..3).each do |i|
      (1..3).each do |j|
         print "*"
      end
   end
   print "\n"
   
   Ans:
   *********
   
   # Problem 2b.
   (1..3).each do |i|
      (1..3).each do |j|
         print "*"
         print "\n"
      end
   end
   
   Ans:
   *
   *
   *
   *
   *
   *
   *
   *
   *
   
   # Problem 2c.
   (1..3).each do |i|
      (1..3).each do |j|
         print "*"
      end
      print "\n"
   end
   
   Ans:
   ***
   ***
   ***
   

7. What is the output?
   

   s = ["cat", "dog", "mouse"]
   t = ""
   s.each do |x|
     t = x + t
   end
   print t, "\n"
   
   Ans:
   mousedogcat
   

8. Find the mistakes in this view and controller code:
   

   -------------- input.html.erb View Code --------------------
   <% form_tag "receipt" %>
   <%= text_field_tag :last_name, "" %>
   <%= text-field-tag :first name, "" >
   <%= text_field_tag : item, "" >
   <%= text_field_tag :price, '' %>
   <%= end %>
   -------------- purchase_controller.rb Controller Code ------
   function purchase 
     first name = params(:first name)
   end
   -------------- receipt.html.erb View Code ------------------
   <h2>Receipt<h1>
   <p>"Thankyou" + <%= first name %> + "for your purchase.</p>
   ------------------------------------------------------------
   
   Corrected Version:
   -------------- input.html.erb View Code --------------------
   <%= form_tag "receipt" %>
   <%= text_field_tag :last_name, "" %>
   <%= text_field_tag :first_name, "" %>
   <%= text_field_tag :item, "" %>
   <%= text_field_tag :price, '' %>
   <% end %>
   -------------- purchase_controller.rb Controller Code ------
   def purchase 
     @first_name = params[:first_name]
   end
   -------------- receipt.html.erb View Code ------------------
   <h2>Receipt<h2>
   <p>Thankyou <%= @first_name %> for your purchase.</p>
   ------------------------------------------------------------
   

9. Convert this style to hex color codes:
   

   body { background-color: rgb(217, 58, 13); }
   Ans:
   body { background-color: #d93a0d; }
   

10. What are the hex color codes for these HTML colors:
     
    
    yellow    purple    lime    olive    teal    silver
    Ans: #ffff00 #800080 #00ff00 #808000 #008080 #c0c0c0

FormHelper vs. FormTagHelper Methods

• Use FormHelper methods when you are using a form to edit a row in a database, or to add a new row to the database.
   
• Use FormTagHelper methods when the piece of data you are inputing does not directly correspond to any field in the database.
   
• References:
   
  api.rubyonrails.org/classes/ActionView/Helpers/FormTagHelper.html
   
  api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html
   
  
  1. Form
      
     FormTagHelper Version:
     

     <% form_tag 'show' do %>
     ... Controls go here.
     <% end %>
     

  FormHelper Version:
  

  <% form_for @item, :url => { :action => 'show' } do |f| %>
  ... Controls go here.
  <% end %>
  

  or shorter:
  

  <% form_for @item, 'show' do |f| %>
  ... Controls go here.
  <% end %>
  

  2. Textfield
      
     FormTagHelper Version:
     

     <%= text_field_tag :celsius, '20', :class => 'tf' %>
     

     :celsius is the name; '20' is the initial value.
      
     FormHelper Version:
     

     <%= f.text_field :celsius, :class => 'tf' %>
     

     :celsius is the field of the database object f.
      
  3. Dropdown Menu
      
     FormTagHelper Version:
      
     

     <%= select_tag :source_rate,
           options_for_select([['Dollars', 1.00000],
                               ['Euro', 1.36749],
                               ['Pesos', 12.6149],
                               ['Pounds', 1.58228]]),
           :class => 'ddm' %>
     

     :source_rate is the name; the first column of the array are the values displayed in the dropdown menu; the second column are the values returned to the controller to be read by a params statement. the option tags are the HTML option tags.
     
      
     FormHelper Version:
     

     <%= f.select :source_rate, 
          [['Dollars', 1.00000],
           ['Euro', 1.36749],
           ['Pesos', 12.6149],
           ['Pounds', 1.58228]],
          :class => 'ddm' %>
     

     :source_rate is the field of the database object f; the values of the dropdown menu are specified in the array as they were in the FormTagHelper version; note that for the FormHelper version, no options_for_select method is needed.
      
  4. Radio Button
      
     FormTagHelper Version:
     

     <%= radio_button_tag :group, value, true %>
     

     :group sets the button group (in a group of radio buttons, only can be checked at a time)
     :value is the value returned to the controller to be read by a params statement
     true means that the radio button should be initially checked.
      
     FormHelper Version:
     

     <%= f.radio_button :group, value, :checked => true %>
     

     :group sets the button group (in a group of radio buttons, only can be checked at a time)
     value is the value returned to the controller to be read by a params statement
     :checked => true means that the radio button should be initially checked.
      
  5. CheckBox
     
      
     FormTagHelper Version:
     

     <%= check_box_tag :sugar, 1, true, :class => 'cb' %>
     

     :sugar is the name of the checkbox
     1 is the value returned to the controller in a params statement
     false means that the checkbox is initially checked.
      
     FormHelper Version:
     

     <%= f.check_box :sugar, 1, :checked => true, :class => 'cb' %>
     

     :sugar is the name of the checkbox
     1 is the value returned to the controller in a params statement, 0 will be returned if the box is not checked.
     :checked => true means that the checkbox is initially checked.
      
  
  
• See the OnlineQuiz and CreditCard (Examples 28 and 29). Use these as examples to help you for Project 5.

Project 5

• Project 5 saves the answers to an online survey in a database table.
   
• Use Rails FormHelper methods to create controls that are each linked to the corresponding database table field.
   
• Like the Rails scaffold statement, a model statement creates the the database design file and associated helper methods for accessing the database. As usual, call rake db:migrate to actually create the database.
   
• Unlike the Rails scaffold statement, a model statement does not write any HTML or CSS code. You must implement the views, layouts, and style file yourself.