To Lecture Notes

IT 231 -- 9/13/12

Review Questions

1. How do you open a Command Prompt Window?
   Ans: Start >> All Programs >> Accessories >> Command Prompt.
   You can also enter Start and type cmd in the box "Search programs and files."
    
2. What are the Command Prompt DOS commands that do the following?
   
   1. Delete a file   Ans: del
   2. Create a new folder.   Ans: mkdir
   3. List all files in a folder.   Ans: dir
   4. Move to the parent folder.   Ans: cd ..
   5. Move to a child folder.   Ans: cd foldername
   6. Move to the root folder on the current drive.   Ans: cd \
   7. Change to a different drive.   Ans: e: if you want to change to drive e.
   8. Show the contents of a file on the screen.   Ans: type filename
   
   
3. List the steps for creating and viewing a Rails project.   Ans:
   
   1. Use the rails command to generate the Rails scripts.
   2. cd into the newly created Rails project folder.
   3. Use rails generate controller to create the controller and views.
   4. Start the server with rails server.
   5. View the project on localhost:3000.


4. List some of the folders created for a Rails project.
   Ans: Folders that we have used so far are app/controllers, app/views, app/assets/images, app/assets/stylesheets. Here is a list of Rails folders.
    
5. What are views? Where are they located?
   Ans: Views are HTML pages that are generated by Rails. A view is created by combining an .html.erb Rails view with a layout to produce the generated page.
    
6. What is the difference between a view and a layout in Ruby on Rails?
   Ans: The view is the content of the page that is normally between the body tags. The layout is everything else on the HTML page.
    
7. Where are images and CSS stylesheets placed in a Rails project?
   Ans: In app/assets/images and app/assets/stylesheets, respectively.
    
8. What is the file extension for view files?
   Ans: .html.erb, where erb means Embedded Ruby.
    
9. What is WEBrick?
   Ans: A localhost server for Rails.
    
10. What is one of the disadvantages of WEBrick?
    Ans: It is slow. Its source code is also completely undocumented, which gives it a bad reputation for some developers.
     
11. What is a method in object oriented programming?
    Ans: It is code that can be called by an object. Methods are also called functions, subroutines, or procedures.

The Anatomy of a Rails URL

• Here is a sample URL for displaying a Rails view:

  http://localhost:3000/photos/pets
  

  http is the protocol
   
  localhost is the server name
   
  3000 is the port number
   
  photos is the controller
   
  pets is the action
   
  
  An action usually means execute a controller method and then show the corresponding view.
  
  
• If the Rails project were posted on an internet server, localhost:3000 would be replaced by the internet address of the server, for example, www.depaul.edu. The Rails URL would then be:
  

  http://www.depaul.edu/photos/pets
  

• To be able to display a view corresponding to an action, this route must be set up in the config/routes.rb file. To display the view associated with controller=photos; action=pets, this route is needed:
  

  get 'photos/pets'
  

• An id will be used later when we are displaying information from databases.
   
• For example

  http://localhost:3000/photos/pets/23
  

  displays the photo with id=23.

Embedded Ruby and Some Helper Functions

• When Ruby statements are embedded within a view or layout file they are called ERB (embedded ruby) statements.
   
  
  Use <%= ... %> to enclose an ERB statement when you want its return value to be placed into the view or layout file.
   
  Use <% ... %> to enclose an ERB statement that does not output to a file, such as control statements.
   
  
• Use this ERB helper function call to embed an image on a web page:
  

  <%= image_tag 'image.jpg' %>
  

  Place the image in the app/assets/images folder.
   
• Look at Example 5 (PageWithImage).
   
• Use this ERB helper function call to to apply a CSS stylesheet to a web page:
  

  <%= stylesheet_link_tag 'styles' %>
  

  Place the stylesheet in the app/assets/stylesheets folder.
   
• Use this ERB helper function call to to create a hyperlink tag:
  

  <%= link_to 'To Page 1', info_page1_path %>
  

  "To Page 1" is the hyperlink text.
  info_page1_page is a Rails helper function that indicates the destination controller as into and the action (destination view) as page1.

Examples

• Look at Examples 6 and 7.

Project 1

• Finish looking at Project 1.
   
• Look at HTML Fonts and Extended HTML Colors for font and color possibilities.

Submitting Projects

• To submit a Rails project:
   
  
  Create a zip file by right clicking on the Rails folder >> Send To >> Compressed (zipped folder)
  
  
• Submit your zipped project on d2l.depaul.edu.