Ruby on Rails What's Ruby A programming language Developed by Yukihiro Matsumoto (aka Matz) in the 1990s What's Rails Initially developed by David Heinemeier Hansson, out of his work on Basecamp, a project management system It is a framework of scripts in ruby that provide for rapid development of web applications, esp those with a database back end Rails can build the skeleton of an application, including the database tables, in just a few commands Ruby Syntax Ruby is largely and loosely based on perl (hence the name, according to lore) Completely object oriented Some Important differences Unlike PHP, scope in variables is defined by the leading sigil the $ sign denotes global scope, not a variable an @ represents local scope within an object instance @@ represents local scope within a class A capitalized name is a constant Historical Differences Javascript--born of the competition between two companies PHP--created by a varied community Ruby--the vision of a single person Rails--the vision of another single person When you compare these, you can see how the starting point influences the process of development Playing on the Command Line Ruby is an interpreter, just like php or bash: Avatar:~ hays$ ruby print "howdy world!" ^d Or, use ruby -e "command": ruby -e 'puts "hello\n"' Or, you can just use irb, which is easier: Avatar:~ hays$ irb >> print "howdy world!" howdy world!=> nil >> Object Oriented Truly Not a prototyping language like javascript Nor a procedural language with OOP bolted on Classes A class is a kind of master object Can contain constants and methods Instances of object can be created from a class, inheriting the traits of the class A simple class class Cat end (but this class doesn't do or mean anything) the class examples are derived from http://www.juixe.com/techknow/index.php/2007/01/22/ruby-class-tutorial/ cat class I want four attributes for a cat; name, color, type, and attribute class Cat # must be capitalized attr_accessor :name, :type, :color, :attribute def initialize(name, type, color, attribute) @name = name @type = type @color = color @attribute = attribute end creating a new cat Now, I can create an instance of the cat class: gc = Cat.new("GC", "short hair", "black", "gimpy") lc = Cat.new("LC", "short hair", "black", "little") add a method I'd like to be able to describe my cats easily So I add a method to the cat class: def describe @name + " is a " + @color + " " + @type + " who is " + @attribute + ".\n" end eliminating con-cat-ination The concatenation is a bit awkward Like php, ruby has a structure for calling variables within a string: "#{@name} is a #{@color} #{@type} who is #{@attribute}.\n" calling the method If I call a cat with the describe method attached, I can get the description of that cat: my_string= gc.describe puts my_string or: puts gc.describe finding cats by name A second method, find_by_name: def self.find_by_name(name) found = nil ObjectSpace.each_object(Cat) { |o| found = o if o.name == name } found end Access Control Methods in a class are public by default Private methods are known only to the individual object Protected methods can only be called by members of the class in which is was defined Variables In ruby, vars are references to objects, not objects themselves So: a = "my value" b=a a[0] = "n" will change both a and b--but if you reassign a, eg a="new value", a is linked to a new object (this might bite you, but it's not likely) Arrays Create an array by assignment: my_array = [ "one", "two", 3, 4 ] Referencing the array: puts "my_array[0] is: #{my_array[0]}\n" The brackets are methods of the array class… Hashes What in php is called an associative array is called a hash in ruby Creating a hash by assignment: my_hash = { 'tree' => 'pine', 'bird' => 'mocking'} puts "\n" puts "my_hash['tree'] is: #{my_hash['tree']}\n" puts "my_hash['bird'] is: #{my_hash['bird']}\n" Notice that the syntax is different walking a hash or array use the each method: a=1 my_hash.each do |key, value| puts "#{a} #{key} is: #{value}" a = a +1 end conditional much like php and javascript, but simpler syntax: a=1 my_hash.each do |key, value| if key == "tree" puts "#{a} #{key} is: #{value}" end a = a +1 end In summary Ruby's syntax is pretty Ruby is all about structure Classes are easy to work with, if you're new, start with simple examples Rails Model View Controller (MVC) Layering again MVC allows a project team to work on different aspects of the application without stepping on each other's toes quite so often Note that neither PHP nor Javascript encourage this, but it can be done in PHP (not so much in Javascript) Rails enforces MVC Model Contains the data of the application Transient Stored (eg Database) Enforces "business" rules of the application Attributes Work flow Views Provides the user interface Dynamic content rendered through templates Three major types Ruby code in erb (embedded ruby) templates xml.builder templates rjs templates (for javascript, and thus ajax) Controllers Perform the bulk of the heavy lifting Handles web requests Maintains session state Performs caching Manages helper modules Convention over Configuration Notion that coding is reduced if we adopt a standard way of doing things Eg., if we have a class "Pet" in our model that defines the characteristic of domestic animal, in rails, the database table created for us will be named "pets" Other chunks of code look for each other by their common names Action Pack Since views and controllers interact so tightly, in rails they are combined in Action Pack Action pack breaks a web request into view components and controller compoents So an action usually involves a controller request to create, read, update, or delete (CRUD) some part of the model, followed by a view request to render a page Processing URLs The basic url used to access a controller is of the form: http://server/controller/action The controller will be one you generate, and the action will be one you've defined in your controller So if you have a controller named "filer" and that controller has an action named "upload", the url will be something like http://127.0.0.1/filer/upload The View The controller will have a folder in app/view named after it, and in that will be the view templates associated with the action methods These templates are usually html with some inserted ruby code While code can be executed in these templates, keep that simple--any data controls should be made in the controller's files Creating a basic site Three commands rails demo cd demo ruby script/generate controller Bark This creates the framework Making it say something A def in the app/controller/bark_controller.rb file: def hello end And some html in the app/views/bark folder, hello.html.erb: <html><head></head> <body> <h3>Howdy</h3> </body> </html> Directory Structure app: most of your code lives here config: information environment and database link database.yml development, test and production versions doc, log, tmp lib: your code, just a place to stick things that don't have a good home elsewhere Directory Structure public: images, javascripts, stylesheets go here script: script that rails uses, most of these are short and reference files in the lib dir for rails vendor: 3rd party code Generating a database site Magic rails temp cd temp rake db:create:all ruby script/generate scaffold Person lname:string fname:string email:string rake db:migrate ruby script/server Sources http://github.com/rails/rails/tree/master/actionpack http://en.wikipedia.org/wiki/Ruby_on_Rails http://www.whytheluckystiff.net/ruby/pickaxe/ http://www.pragprog.com/titles/rails3/agile-webdevelopment-with-rails-third-edition http://www.juixe.com/techknow/index.php/2007/01 /22/ruby-class-tutorial/