Ruby on Rails Creating a Rails Application

1
Ruby on RailsCreating a Rails Application

• Carol E Wolf
• CS396X

2
Ruby Console Window

• First choose Rails Applications
• Next select Open Ruby Console Window
• At the prompt, type
• rails apps_name
• For example rails library
• This creates a full directory system in the
  folder rails_apps.

• Console Window

3
Rails directory system
4
Important folders

• app
• controllers sits between client and database
• helpers module with common ruby code
• models code to interface with the database
• views web pages containing html and erb
• db contains database
• migration methods to change the database
• script
• console interactive console window for ruby
  code
• dbconsole interactive console window for the
  database
• generate methods to generate scaffolding and
  migrations
• server activates server to be used with
  localhost

5
Adding a table to the database

• You can use the scaffold command to set up your
  database.
• The database is created when you create the
  application.
• Type the following to create a table called
  books.
• ruby script/generate scaffold book isbnstring
  authorstring titlestring
• Note that if you call it book, rails
  automatically makes it books.
• This creates the file 20080805165427_create_books.
  rb in the db/migrate folder, where the numbers
  are a time stamp.
• Then type
• rake dbmigrate
• The rake command executes all the ruby files in
  the migrate folder.
• Rails includes a primary id field that is
  automatically incremented when you add rows to
  the database.

6
The file, schema.rb

• Rake adds a ruby file to the db folder called
  schema. Lines beginning with are comments.
• This file is auto-generated from the current
  state of the database.
• (Additional comments omitted.)
•  
• ActiveRecordSchema.define(version gt
  20080805165427) do
•  
• create_table "books", force gt true do t
• t.string "isbn"
• t.string "author"
• t.string "title"
• t.datetime "created_at"
• t.datetime "updated_at"
• end
•  end

7
View the contents of the database

• To begin with, the books table is empty. Bring
  up the server to access it.
• ruby script/server
• The server that comes with InstantRails is called
  mongrel. It is a version of the open source
  apache server.
• Point your browser to
• http//localhost3000/books where localhost is
  the name for the IP address 127.0.0.1. (Use that
  if your computer does not recognize localhost.)
• localhost is often called the local loop.

8
The first web page

• The first web page is just the title of the
  table.
• It includes a heading and a link to a New book
  page.
• Click it to add data to the table.

9
The New book page

• The new book page provides text fields with
  labels.
• You can use these to add data.
• Just fill in the fields and click Create.
• When done, it will take you to a third page that
  shows what you added.

10
The show page and the index after adding a book
to the table.
11
The index.html.erb page uses embedded ruby code.

• lth1gtListing bookslt/h1gt
• lttablegt
• lttrgt
• ltthgtIsbnlt/thgt
• ltthgtAuthorlt/thgt
• ltthgtTitlelt/thgt
• lt/trgt
• lt for book in _at_books gt
• lttrgt
• lttdgtlth book.isbn gtlt/tdgt
• lttdgtlth book.author gtlt/tdgt
• lttdgtlth book.title gtlt/tdgt
• lttdgtlt link_to 'Show', book gtlt/tdgt
• lttdgtlt link_to 'Edit', edit_book_path(book)
  gtlt/tdgt
• lttdgtlt link_to 'Destroy', book, confirm gt
  'Are you sure?', method gt delete gtlt/tdgt
• lt/trgt
• lt end gt
• lt/tablegt

12
Explanation of some of the index page code

• The lttablegt tag creates a table with headers
  enclosed by ltthgtlt/thgt , rows by lttrgtlt/trgt, and
  columns by lttdgtlt/tdgt
• The embedded ruby code is enclosed by lthgt
• lth book.isbn gt
• This line displays the data in the book column.
• The controller retrieves the data in a result
  set, a two dimensional array. It is displayed on
  the page using a for loop.
• lt for book in _at_books gt
• The _at_ sign is used to indicate a variable.
• The lt link_to 'New book', new_book_path gt line
  generates the html code lta href"/books/new"gtNew
  booklt/agt .

13
Header code added by rails to the beginning of
the web pages. It also adds a foot to the end.

• lt!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
  Transitional//EN" "http//www.w3.org/TR/xhtml1/DTD
  /xhtml1-transitional.dtd"gt
• lthtml xmlns"http//www.w3.org/1999/xhtml"
  xmllang"en" lang"en"gt
• ltheadgt
• ltmeta http-equiv"content-type"
  content"text/htmlcharsetUTF-8" /gt
• lttitlegtBooks indexlt/titlegt
• ltlink href"/stylesheets/scaffold.css?121794806
  8" media"screen" rel"stylesheet"
  type"text/css" /gt
• lt/headgt
• ltbodygt
• ltp style"color green"gtlt flashnotice gtlt/pgt