Ruby On Rails Introduction

1
Ruby On Rails Introduction
2
What is Ruby On Rails (RoR)?

• Its a free web application framework
• It is based on the Ruby language
• It allows for web projects to be developed
  quickly, simply and efficiently

3
RoR History

• Came from web based project management software
  (Basecamp)

4
RoR History II

• Extracted by David Hansson of 37Signals
• Basecamp allowed a centralised approach to
  project management software
• Basecamp comes with an API for integration into
  other software
• It was a simple way of managing projects project
  flow, milestones, to-do lists etc
• RoR went public in 2004
• In 2007 apple shipped OSX (Leopard) with RoR

5
RoR philosophy

• RoR was designed to make life as simple as
  possible
• This increases productivity
• Reduces initial learn time
• Makes managing, debugging easier
• The convention used makes working on projects
  with multiple coders easier
• Less decisions need to be made because of this
  convention

6
What is Ruby?

• Ruby is the language that RoR is based on
• It is purely object orientated
• Originated in Japan in the 90s

7
What is Rails?

• It is a framework for the Ruby language
• It is designed for web based applications with a
  database back-end
• These are very common in the WWW
• Are becoming more popular

8
Why is this technology so popular?

• Standalone software is decreasing in popularity
• Centralisation of software makes sense
• Distribution can be controlled easily when
  centralised
• User access can be controlled
• Updating of software becomes much easier

9
Software Centralisation

• Can give cheaper per unit costs
• Reduction in the administration of software
• Support costs adhere to economies of scale
• The more people using the software means that the
  costs per user reduces

10
Installation

• RoR has been a pain to install in older years
• Especially true on OSX
• Easy now that OSX comes with preinstalled
• For Win users there is an all in one installer
  for Ruby http//rubyinstaller.rubyforge.org/

11
Win Installation
12
The development family

• Various tools are used to develop RoR
  applications
• These include
• Ruby
• Rails
• MySQL, SQLite3.
• Mongrel
• Capistrano
• Subversion
• Each of these has its own subsets of tools

13
MySQL

• We have already mentioned MySQL for databases
• This is a good choice for RoR and its free!
• This needs to be installed and set up
• Download some tools which allow you to
  graphically manipulate your databases. Its
  easier!!

14
MySQL GUIs

• For windows you can use the Control Center
• For OSX you can use CocoaMySQL
• You can make a web/server based GUI such as
  PHPmyAdmin. You may have seen and used this on
  the University server http//www.cs.cf.ac.uk/phpMy
  Admin/

15
Mongrel

• Mongrel is the server that RoR uses
• Or rather that the Ruby web apps use
• Uses HTTP for its serving. We should remember
  this protocol from before!
• Not based on Common Gateway Interface (CGI) which
  can be used to interface with applications for
  the web

16
Capistrano

• Capistrano can be used to deploy your RoR
  application
• It was originally called SwitchTower
• It allows you to execute commands over multiple
  servers.
• It is dynamic so can interact with the output
  from servers

17
Subversion

• Subversion is a Version Control System
• This allows you to write code in a controlled
  manner along with other coders
• Code can be rolled back if necessary
• All updates to the code are time stamped and
  commented
• The only way for multiple coders to work on the
  same project

18
RoR

• RoR is based on 2 main principles
• Content over Configuration
• Dont repeat yourself

19
Content over Configuration

• "Convention over Configuration" means a developer
  only needs to specify unconventional aspects of
  the application. For example, if there's a class
  Sale in the model, the corresponding table in the
  database is called sales by default.
• It is only if one deviates from this convention,
  such as calling the table "products_sold", that
  one needs to write code regarding these names.
  Wikipedia

20
Dont repeat yourself

• Don't Repeat Yourself (DRY, also known as Single
  Point of Truth) is a process philosophy aimed at
  reducing duplication, particularly in computing.
• The philosophy emphasizes that information should
  not be duplicated, because duplication increases
  the difficulty of change, may decrease clarity,
  and leads to opportunities for inconsistency.
  Wikipedia

21
Model-View-Controller (MVC)

• The Rails framework uses the MVC architecture
• Use of the MVC architecture should keep the
  Business Logic and the User Interface seperated
  to an extent
• This allows one to be altered or updates without
  affecting the other

22
Business Logic

• This is the way that databases interact with the
  User Interface
• They control how data is gathered, manipulated
  and passed about
• They are in essence the algorithms which do the
  clever bits with the data (if there are any!)

23
The MVC Model

• The business logic just mentioned is a part of
  the Model
• Along with this is the data that it interacts with

24
The MVC Diagram
25
The MVC View

• The view is geared at the User Interface
• This can be the text on the page
• Your input devices such as text boxes etc

26
The MVC Controller

• This interfaces between the model and the view
• It lets the model know what the user is doing in
  the view
• This can be user input from the mouse or the
  keyboard

27
MVC for web applications

• Model - The data in the database and the
  algorithms used to manipulate it
• View - The front end HTML pages
• Controller - Gathers the data based on user input
  thats used as content for the HTML

28
The MVC Cycle

• The user interacts with the user interface in
  some way (e.g. presses a button).
• A controller handles the input event from the
  user interface, often via a registered handler or
  callback.
• The controller notifies the model of the user
  action, possibly resulting in a change in the
  model's state. (e.g. controller updates user's
  Shopping cart).
• A view uses the model (indirectly) to generate an
  appropriate user interface (e.g. the view
  produces a screen listing the shopping cart
  contents). The view gets its own data from the
  model. The model has no direct knowledge of the
  view.
• The user interface waits for further user
  interactions, which begins the cycle anew.
  Wikipedia

29
Scaffolding

• In RoR scaffolding helps speed up development of
  the connectivity between the database and the
  user interface
• It provides a basic set up from which you can
  build your application
• Called scaffolding because as you build up your
  app you remove the scaffolding (akin to house
  building!)
• It can create all of the read, write, delete etc
  code and associated front end for database apps.
  We will see this later
• In the MVC this will create the models and views
  that we need to get started

30
Rake

• This is a ruby specific make tool
• If you have programmed in other languages you may
  have used make before
• Used extensively in C coding
• If you have many files in a project then when
  compiling there is only the need to recompile
  files that have changed and their dependants
• Make does this
• Rake is a similar tool for building ruby code
• Uses Rakefiles to control how it works

31
A simple application
32
Scaffolding

• This simple example is created using the RoR
  scaffolding
• Remember this is the basics of a project for you
  to build from

33
How does it work?

• The show hyperlink
• When clicked this executes ruby code
• The hyperlink points to http//localhost3000/even
  ts/1
• The link issues a GET request for the event at
  that address
• This is how the appropriate ruby code gets
  executed
• This is all based on conventions making
  development for us quicker as all the code can be
  generated for us

34
Controller

• This GET request for that particular event fires
  the controller
• This is how the front end communicates with the
  database and business logic
• This will go and get the necessary data from the
  database to display on the HTML page for show

35
Views

• We have now fetched the data that we need from
  the database
• And the ruby code found in the app/views part of
  our application lets us create the HTML

36
Creating HTML

• ltpgt
• ltbgtNamelt/bgt
• lt h _at_event.name gtlt/pgt
• ltpgt
• ltbgtBudgetlt/bgt
• lt h _at_event.budget gt
• lt/pgt
• lt link_to 'Edit', edit_event_path(_at_event)
• lt link_to 'Back', events_path gt

Retrieved database data
Ruby code
Create URLS based on naming conventions