ruby for c# developers
DESCRIPTION
This was a presentation from 2006 for the St. Louis Code Camp presenting Ruby for C# Developers and showing the power of Ruby interacting with .NET.TRANSCRIPT
St. Louis Code CampMay 6th, 2006
Ruby for C# Developers Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Cory Foyhttp://www.cornetdesign.com
St. Louis Code Camp
May 6th, 2006
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Overview
• What is Ruby?
• Ruby Basics
• Advanced Ruby
• Ruby and .NET integration
• Wrap-up
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
What is Ruby?
• First released in 1995 by Yukihiro Matsumoto (Matz)
• Object-Oriented– number = 1.abs #instead of Math.abs(1)
• Dynamically Typed– result = 1+3
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
What is Ruby?
• http://www.rubygarden.org/faq/entry/show/3
class Person attr_accessor :name, :age # attributes we can set and retrieve def initialize(name, age) # constructor method @name = name # store name and age for later retrieval @age = age.to_i # (store age as integer) end def inspect # This method retrieves saved values "#@name (#@age)" # in a readable format end end
p1 = Person.new('elmo', 4) # elmo is the name, 4 is the age puts p1.inspect # prints “elmo (4)”
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Will It Change Your Life?
• Yes!
• Ok, Maybe
• It’s fun to program with
• And what is programming if it isn’t fun?
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics
• Variables, Classes and Methods
• Properties / Attributes
• Exceptions
• Access Control
• Importing Files and Libraries
• Duck Typing
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Variables• Local (lowercase, underscores)
– fred_j = Person.new(“Fred”)• Instance (@ sign with lowercase)
– @name = name• Class (@@ with lowercase)
– @@error_email = “[email protected]”• Constant (Starts with uppercase)
– MY_PI = 3.14– class Move
• Global ($ with name)– $MEANING_OF_LIFE = 42
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Classes
• Class definitions are started with class,are named with a CamelCase name, and ended with end
class Move attr_accessor :up, :right def initialize(up, right) @up = up @right = right endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Classes
• Attributes and fields normally go at the beginning of the class definition
class Move attr_accessor :up, :right def initialize(up, right) @up = up @right = right endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Classes
• initialize is the same concept as a constructor from .NET or Java, and is called when someone invokes your object using Move.new to set up the object’s state
class Move attr_accessor :up, :right def initialize(up, right) @up = up @right = right endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Methods
• Methods return the last expression evaluated. You can also explicitly return from methods
class Move def up @up end
def right return @right endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Methods
• Methods can take in specified parameters, and also parameter lists (using special notation)
class Move def initialize(up, right) @up = up @right = right endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Methods
• Class (“Static”) methods start with either self. or Class.
class Move def self.create return Move.new end
def Move.logger return @@logger endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Properties
• Like .NET, Ruby supports the concept of Properties (called Attributes)
class Move def up @up endend
class Move def up=(val) @up = val endend
move = Move.newmove.up = 15puts move.up #15
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Properties
• Unlike .NET, Ruby provides convenience methods for doing this
class Move attr_accessor :up #Same thing as last slideend
move = Move.newmove.up = 15puts move.up #15
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Properties
• You can specify read or write only attributes as well
class Move attr_reader :up #Can’t write attr_writer :down #Can’t readend
move = Move.newmove.up = 15 #errord = move.down #error
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Exceptions
• Ruby has an Exception hierarchy
• Exceptions can be caught, raised and handled
• You can also easily retry a block of code when you encounter an exception
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Exceptionsprocess_file = File.open(“testfile.csv”)
begin #put exceptional code in begin/end block #...process file rescue IOError => io_error puts “IOException occurred. Retrying.” retry #starts block over from begin rescue => other_error puts “Bad stuff happened: “ + other_error else #happens if no exceptions occur puts “No errors in processing. Yippee!” ensure # similar to finally in .NET/Java process_file.close unless process_file.nil?end
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Access Control
• Ruby supports Public, Protected and Private methods
• Private methods can only be accessed from the instance of the object, not from any other object, even those of the same class as the instance
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Access Control
• Access is controlled by using keywordsclass Move private def calculate_move end #Any subsequent methods will be private until.. public def show_move end #Any subsequent methods will now be publicend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Access Control
• Methods can also be passed as argsclass Move def calculate_move end
def show_move end
public :show_move protected :calculate_moveend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Imports
• To use a class from another file in your class, you must tell your source file where to find the class you want to userequire ‘calculator’class Move def calculate_move return @up * Calculator::MIN_MOVE endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics - Imports• There are two types of imports
– require• Only loads the file once
– load• Loads the file every time the method is executed
• Both accept relative and absolute paths, and will search the current load path for the file
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• What defines an object?
• How can you tell a car is a car?– By model?– By name?
• Or, by it’s behavior?
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• We’d use static typing! So only the valid object could be passed in
• What if my object has the same behavior as a Car?
class CarWash def accept_customer(car)
endend
• How would we validate this in .NET or Java?
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• What is this?
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• How about this?
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• What about this?
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• We know objects based on the behaviors and attributes the object possesses
• This means if the object passed in can act like the object we want, that should be good enough for us!
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Duck Typing
• Or we could just let it fail as a runtime error
Class CarWash def accept_customer(car) if car.respond_to?(:drive_to)
@car = carwash_car
elsereject_customer
end endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• In a static-typed language, how do we use the compiler?– Find misspellings– Find improper usage– Enforce contracts– Find missing semicolons
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• What is a Unit Test?
• “In computer programming, a unit test is a procedure used to validate that a particular module of source code is working properly.” (Wikipedia)
• Sounds like our compiler is just a unit testing mechanism!
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests• Ruby comes built in with a Unit Testing
framework – Test::Unit– Create individual tests– Create test suites– Invoke our tests and suites
• Using this framework and Test-Driven Development, we can have a high confidence level in our code
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• Let’s build a toaster!
• Should be able to have toasting levels set
• Should heat the bread based on the toasting levels
• Different breads have different cooking times.
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• Let’s start with a basic testclass TestToaster < Test::Unit::TestCase def test_toast_bread toaster = Toaster.new bread = WonderBread.new toaster.heat_level = 5 toaster.toast(bread) assert_equal(“Nicely toasted”, bread.status) endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• And run itroot@dilbert $ruby testtoaster.rbLoaded suite testtoasterStartedEFinished in 0.0 seconds.
1) Error:test_toast_bread(TestToaster):NameError: uninitialized constant TestToaster::Toaster testtoaster.rb:4:in `test_toast_bread'
1 tests, 0 assertions, 0 failures, 1 errors
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests• Next, let’s build our objects to allow our
test to runclass Toaster attr_accessor :heat_level def toast(bread) endend
class WonderBread attr_accessor :statusend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• And run themroot@dilbert $ruby testtoaster.rbLoaded suite testtoasterStartedFFinished in 0.093 seconds.
1) Failure:test_toast_bread(TestToaster) [testtoaster.rb:10]:<"Nicely toasted"> expected but was<nil>.
1 tests, 1 assertions, 1 failures, 0 errors
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• Finally, let’s make the test passclass Toaster def toast(bread) bread.status = “Nicely toasted” endend
root@dilbert $ruby testtoaster.rbLoaded suite testtoasterStarted.Finished in 0.0 seconds.
1 tests, 1 assertions, 0 failures, 0 errors
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• We then keep writing tests to drive the behavior of the code we want to write
• A side benefit is we get a suite of regression tests for our code
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Unit Tests
• How did the compiler help us again?– Find misspellings (Unit Tests)– Find improper usage (Unit Tests)– Enforce contracts (Duck Typing)– Find missing semicolons (No
semicolons! ;))
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Modules
• Blocks and Iterators
• Modules
• Mixins / Inheritance
• Reflection
• Other Goodies
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Blocks
• A block is just a section of code between a set of delimters – { } or do..end
{ puts “Ho” }
3.times do puts “Ho “end #prints “Ho Ho Ho”
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Blocks• Blocks can be associated with method invocations.
The methods call the block using yield
def format_print puts “Confidential. Do Not Disseminate.” yield puts “© SomeCorp, 2006”end
format_print { puts “My name is Earl!” } -> Confidential. Do Not Disseminate. -> My name is Earl! -> © SomeCorp, 2006
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Blocks• Methods can act like the using statement
from .NET using blocks
def MyConnection.open(*args) conn = Connection.open(*args) if block_given? yield conn #passes conn to the block conn.close #closes conn when block finishes end
return connend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Iterators
• Iterators in Ruby are simply methods that can invoke a block of code
• Iterators typically pass one or more values to the block to be evaluated
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Iteratorsdef fib_up_to(max) i1, i2 = 1, 1 while i1 <= max yield i1 i1, i2 = i2, i1+i2 # parallel assignment endend
fib_up_to(100) {|f| print f + “ “}
-> 1 1 2 3 5 8 13 21 34 55 89
• Pickaxe Book, page 50
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Modules• At their core, Modules are like
namespaces in .NET or Java.module Kite def Kite.fly endend
module Plane def Plane.fly endend
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Mixins
• Modules can’t have instances – they aren’t classes
• But Modules can be included in classes, who inherit all of the instance method definitions from the module
• This is called a mixin and is how Ruby does “Multiple Inheritance”
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Mixinsmodule Print def print puts “Company Confidential” yield endend
class Document include Print #...end
doc = Document.newdoc.print { “Fourth Quarter looks great!” } -> Company Confidential -> Fourth Quarter looks great!
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Reflection
• How could we call the Length of a String at runtime in .NET?
String myString = "test";int len = (int)myString
.GetType()
.InvokeMember("Length", System.Reflection.BindingFlags.GetProperty,
null, myString, null);Console.WriteLine("Length: " + len.ToString());
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Reflection
• In Ruby, we can just send the command to the object
myString = “Test”puts myString.send(:length) # 4
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Advanced Ruby - Reflection
• We can also do all kinds of fancy stuff#print out all of the objects in our systemObjectSpace.each_object(Class) {|c| puts c}
#Get all the methods on an object“Some String”.methods
#see if an object responds to a certain methodobj.respond_to?(:length)
#see if an object is a typeobj.kind_of?(Numeric)obj.instance_of?(FixNum)
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Basics – Other Goodies
• RubyGems – Package Management for Ruby Libraries
• Rake – A Pure Ruby build tool (can use XML as well for the build files)
• RDoc – Automatically extracts documentation from your code and comments
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby and .NET
• Why?– Provide Scripting ability in your apps– Quickly prototype– Class Introspection
• What about JScript.NET?– Ruby is cross platform– JScript might be better choice
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby and .NET
• Three projects in the works
• Ruby to .NET Bridge– http://rubydotnet.sourceforge.net/
• MS Funded Ruby CLR project– http://www.plas.fit.qut.edu.au/rubynet/
• RubyCLR– http://rubyforge.org/projects/rubyclr
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby and .NET
• Bridge Example– Basic Arrays– Interacting with Objects– Creating Forms– Attaching to Events
St. Louis Code CampMay 6th, 2006
Cory Foyhttp://www.cornetdesign.com
Ruby for C# Developers
Ruby Resources• Programming Ruby by Dave Thomas (the
Pickaxe Book)• http://www.ruby-lang.org• http://www.rubyforge.org• http://www.rubycentral.org• http://www.ruby-doc.org• http://www.rubygarden.org• http://www.stlruby.org