Learning Ruby Programming Fundamentals

Ruby

IRB(Interactive Ruby) irb(main):001:0> irb(main):001:0> 1 + 1 2 puts "Hello, World!!" $ ruby hello.rb

/* PHP */ $i = 1; echo "Value is " + $i # 1 # Ruby i=1 puts "Value is " + i #TypeError: can't convert Fixnum into String # from (irb):2:in `+' # from (irb):2 /* C */ int a = 5; float b = a;

Integer Float 5 -205 9999999999 0 54.321 0.001 -12.312 0.0

puts 1.0 + 2.0 puts 2.0 * 3.0 puts 5.0 - 8.0 puts 9.0 / 2.0 puts 1 + 2 puts 2 * 3 puts 5 - 8 puts 9 / 2 # 3.0 # 6.0 # -3.0 # 4.5 # 3 # 6 # -3 # 4 puts 5 * (12-8) + -15 puts 98 + (59872 / (13*8)) * -52

String puts 'Hello, world!' puts '' puts 'Good-bye.' var1 = 'stop' var2 = 'foobar' var3 = "aAbBcC" puts 'I like ' + 'apple pie.' puts 'You\'re smart!' puts var1.reverse # 'pots' puts var2.length # 6 puts var3.upcase puts var3.downcase puts '12' + 12 #<TypeError: can't convert Fixnum into String>

Ruby # "UPPER" puts "upper".upcase # -5 puts -5.abs # Fixnum puts 99.class # "Ruby Rocks!" 5.times do puts "Ruby Rocks!" end

Local Variable composer = 'Mozart' puts composer + ' was "da bomb", in his day.' my_composer = 'Beethoven' puts 'But I prefer ' + my_composer + ', personally.'

Conversions var1 = 2 var2 = '5' puts var1.to_s + var2 # 25 puts var1 + var2.to_i # 7 puts 9.to_f / 2 # 4.5

Constant Foo = 1 Foo = 2 # (irb):3: warning: already initialized constant Foo RUBY_PLATFORM # => "x86_64-darwin10.7.0" ENV # => { "PATH" => "....", "LC_ALL" => "zh_TW.UTF-8" }

nil nil # nil nil.class # NilClass nil.nil? # true 42.nil? # false nil == nil # true false == nil # false

Comment # this is a comment line # this is a comment line =begin This is a comment line This is a comment line =end

Array colors = ["red", "blue"] a = [ 1, "cat", 3.14 ] colors.push("black") colors << "white" puts colors.join(", ") # red, blue, black, white puts a[0] # 1 puts a.size # 3 a[2] = nil puts a.inspect # [1, "cat", nil] a[99] # nil colors.pop puts colors.last #black

Hash config = { "foo" => 123, "bar" => 456 } puts config["foo"] # 123 config["nothing"] # nil config = { foo: 123, bar: 456 } # { :foo => 123, :bar => 456 }

Symbols config = { :foo => 123, :bar => 456 } puts config[:foo] # 123 "foobar".object_id # 2151854740 "foobar".object_id # 2151830100 :foobar.object_id # 577768 :foobar.object_id # 577768

puts 1 > 2 # puts 1 < 2 # puts 5 >= 5 # puts 5 <= 4 # puts 1 == 1 # puts 2 != 1 # puts ( 2 > 1 ) && ( 2 > 3 ) # puts ( 2 > 1 ) || ( 2 > 3 ) #

If if account.total > 100000 puts "large account" elsif account.total > 25000 puts "medium account" else puts "small account" End puts "greater than ten" if total > 10

x = 3 if x > 3 y = "foo" else y = "bar" End x = 3 y = ( x > 3 )? "foo" : "bar"

Case case name when "John" puts "Howdy John!" when "Ryan" puts "Whatz up Ryan!" else puts "Hi #{name}!" end

# while i=0 while ( i < 10 ) i += 1 next if i % 2 == 0 # End # loop i = 0 loop do i += 1 break if i > 10 # end # until i = 0 i += 1 until i > 10 puts i # 11

True or False puts "not execute" if nil puts "not execute" if false puts "execute" if true # execute puts "execute" if # execute ( JavaScript ) puts "execute" if 0 # execute ( C ) puts "execute" if 1 # execute puts "execute" if "foo" # execute puts "execute" if Array.new # execute

Methods def say_hello(name) result = "Hi, " + name return result end puts say_hello('ihower') # Hi, ihower def say_hello(name) "Hi, " + name end say_hello 'ihower'

?! array=[2,1,3] array.empty? # false array.sort # [1,2,3] array.inspect # [2,1,3] array.sort! # [1,2,3] array.inspect # [1,2,3]

Classes color_string = String.new color_string = "" # color_array = Array.new color_array = [] # color_hash = Hash.new color_hash = {} # time = Time.new # puts time

Classes class Person # p1 = Person.new("ihower") p2 = Person.new("ihover") def initialize(name) # @name = name # end p1.say("Hello") # Hello, ihower p2.say("Hello") # Hello, ihover def say(word) puts "#{word}, #{@name}" # end end

class MyClass def public_method end private def private_method end protected def protected_method end end

Class class Pet class Dog < Pet attr_accessor :name, :age def say(word, person) puts "Bark at #{person}!" def say(word) super(word) puts "Say: #{word}" end end end end Cat.new.say("Hi") class Cat < Pet Dog.new.say("Hi", "ihower") def say(word) puts "Meow~" super Meow~ end Say: Hi end Bark at ihower! Say: Hi

Iterator # 1.upto(9) { |x| puts x } languages = ['Ruby', 'Javascript', 'Perl'] languages.each do |lang| puts "I love #{lang}!" end # languages = ['Ruby', 'Javascript', 'Perl'] languages.each_with_index do |lang, i| puts "#{i}, I love #{lang}!" end # 0, I Love Ruby # 1, I Love Javascript # 2, I Love Perl # I Love Ruby # I Love Javascript # I Love Perl # 3.times do puts 'Good Job!' end # Good Job! # Good Job! 3.times { puts "Hello" } # Good Job!

Iterator # [2,1,3].sort! { |a, b| b <=> a } # [3, 2, 1] # a = [ "a", "b", "c", "d" ] b = a.map {|x| x + "!" } puts b.inspect # ["a!", "b!", "c!", "d!"] # (5..10).inject {|sum, n| sum + n } # b = [1,2,3].find_all{ |x| x % 2 == 0 } # find the longest word longest = ["cat", "sheep", "bear"].inject do |memo,word| ( memo.length > word.length )? memo : word end b.inspect # [2] # a = [51, 101, 256] a.delete_if {|x| x >= 100 } # [51]

Iterator file = File.new("testfile", "r") # ... file.close File.open("testfile", "r") do |file| # ... end #

Yield # def call_block puts "Start" yield yield puts "End" end call_block { puts "Blocks are cool!" } # # "Start" # "Blocks are cool!" # "Blocks are cool!" # "End"

Yield def call_block yield(1) yield(2) yield(3) end call_block { |i| puts "#{i}: Blocks are cool!" } # # "1: Blocks are cool!" # "2: Blocks are cool!" # "3: Blocks are cool!"