cory foy st. louis code camp may 6th, 2006 ruby for c# developers cory foy st. louis code camp

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

Overview

• What is Ruby?

• Ruby Basics

• Advanced Ruby

• Ruby and .NET integration

• Wrap-up

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

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)”

Will It Change Your Life?

• Yes!

• Ok, Maybe

• It’s fun to program with

• And what is programming if it isn’t fun?

Ruby Basics

• Variables, Classes and Methods

• Properties / Attributes

• Exceptions

• Access Control

• Importing Files and Libraries

• Duck Typing

Ruby Basics - Variables• Local (lowercase, underscores)

– fred_j = Person.new(“Fred”)• Instance (@ sign with lowercase)

– @name = name• Class (@@ with lowercase)

– @@error_email = “testing@test.com”• Constant (Starts with uppercase)

– MY_PI = 3.14– class Move

• Global ($ with name)– $MEANING_OF_LIFE = 42

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

• Attributes and fields normally go at the beginning of the class definition

• 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

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

• Methods can take in specified parameters, and also parameter lists (using special notation)

class Move def initialize(up, right) @up = up @right = right endend

• Class (“Static”) methods start with either self. or Class.

class Move def self.create return Move.new end

def Move.logger return @@logger endend

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

• 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

• 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

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

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

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

• 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

• Methods can also be passed as argsclass Move def calculate_move end

def show_move end

public :show_move protected :calculate_moveend

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

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

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?

• 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?

• What is this?

• How about this?

• What about this?

• 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!

• 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

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

• 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!

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

• 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.

• 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

• 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

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

• 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>.

• 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.

• 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

• 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! ;))

Advanced Ruby - Modules

• Blocks and Iterators

• Modules

• Mixins / Inheritance

• Reflection

• Other Goodies

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”

Advanced Ruby - Blocks• Blocks can be associated with method invocations.

The methods call the block using yield

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

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

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

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

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”

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!

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());

• In Ruby, we can just send the command to the object

myString = “Test”puts myString.send(:length) # 4

• 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)

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

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

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

Ruby and .NET

• Bridge Example– Basic Arrays– Interacting with Objects– Creating Forms– Attaching to Events

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

cory foy st. louis code camp may 6th, 2006 ruby for c# developers cory foy st. louis code camp

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