Ruby for Perl Programmers

1. Ruby for Perl programmers for Perl programmers Ruby All material Copyright Hal E. Fulton, 2002. Use freely but acknowledge the source.

20. A Simple Class class Person def initialize(name, number) @name, @phone = name, number end def inspect “ Name=#{@name} Phone=#{@phone}” end end # Note that “new” invokes “initialize” a1 = Person.new(“Bill Gates”, “1-800-666-0666”) a2 = Person.new(“Jenny”, “867-5309”) # p is like print or puts but invokes inspect p a2 # Prints “Name=Jenny Phone=867-5309”

21. Defining attributes # Adding to previous example… class Person attr_reader :name # Defines a “name” method attr_accessor :phone # Defines “phone” and # “phone=“ methods end person1 = a2.name # “Jenny” phone_num = a2.phone # “867-5309” a2.phone = “512 867-5309” # Value replaced… p a2 # Prints “Name=Jenny Phone=512 867-5309”

22. Class-level entities class Foobar @@count = 0 # Class variable def initialize(str) @data = str @@count += 1 end def Foobar.population # Class method @@count end end a = Foobar.new(“lions”) b = Foobar.new(“tigers”) c = Foobar.new(“bears”) puts Foobar.population # Prints 3

23. Inheritance class Student < Person def initialize(name, number, id, major) @name, @phone = name, number @id, @major = id, major end def inspect super + “ID=#@id Major=#@major” end end x = Student.new(“Mike Nicholas”, “555-1234”, “ 000-13-5031”, “physics”) puts “yes” if x.is_a? Student # yes puts “yes” if x.is_a? Person # yes

24. Singleton objects # Assume a “Celebrity” class newsguy = Celebrity.new(“Dan Rather”) popstar = Celebrity.new(“Britney Spears”) superman = Celebrity.new(“Superman”) class << superman def fly puts “Look, I’m flying! Woo-hoo!” end end superman.fly # Look, I’m flying! Woo-hoo! newsguy.fly # Error!

26. Using method_missing class OSwrapper def method_missing(method, *args) system(method.to_s, *args) end end sys = OSwrapper.new sys.date # Sat Apr 13 16:32:00… sys.du “-s”, “/tmp” # 166749 /tmp

31. Module example 1 class MyCollection include Enumerable # interface polymorphism #… def <=>(other) # Compare self to other somehow… # Return –1, 0, or 1 end def each # Iterate through the collection and do # a yield on each one… end end

32. Module example 2 # Namespace management def sin puts “Pride, gluttony, bad commenting…” end x = Math.sin(theta) # unrelated to “our” sin User = Process.uid # uid of this process

33. Module example 3 # A user-defined module module FlyingThing def fly puts “Look, I’m flying!” end end class Bat < Mammal include FlyingThing # A substitute for MI? #… end x = Bat.new x.is_a? Bat # true x.is_a? Mammal # true x.is_a? FlyingThing # true

52. Example: Existential Quantifiers module Quantifier def any? self.each { |x| return true if yield x } false end def all? self.each { |x| return false if not yield x } true end end class Array include Quantifier end list = [1, 2, 3, 4, 5] flag1 = list.any? {|x| x > 5 } # false flag2 = list.any? {|x| x >= 5 } # true flag3 = list.all? {|x| x <= 10 } # true flag4 = list.all? {|x| x % 2 == 0 } # false

70. The Ruby Way Table of Contents 1. Ruby in Review 2. Simple Data Tasks 3. Manipulating Structured Data 4. External Data Manipulation 5. OOP and Dynamicity in Ruby 6. Graphical Interfaces for Ruby 7. Ruby Threads 8. Scripting and System Administration 9. Network and Web Programming A. From Perl to Ruby B. From Python to Ruby C. Tools and Utilities D. Resources on the Web (and Elsewhere) E. What’s New in Ruby 1.8 More than 300 sections More than 500 code fragments and full listings More than 10,000 lines of code All significant code fragments available in an archive

71. exit(0) # That’s all, folks!