Ruby 程式語言簡介

IRB(Interactive Ruby)

irb(main):001:0>irb(main):001:0> 1 + 1Þ2

puts "Hello, World!!"

$ ruby hello.rb

程式語言分類/* PHP */$i = 1;echo "Value is " + $i# 1

/* C */int a = 5;float b = a;

# Rubyi=1puts "Value is " + i

#TypeError: can't convert Fixnum into String# from (irb):2:in `+'# from (irb):2

整數 Integer 浮點數 Float

54.3210.001-12.3120.0

5-20599999999990

四則運算puts 1.0 + 2.0puts 2.0 * 3.0puts 5.0 - 8.0puts 9.0 / 2.0

# 3.0# 6.0# -3.0# 4.5

puts 1 + 2puts 2 * 3puts 5 - 8puts 9 / 2

# 3# 6# -3# 4

puts 5 * (12-8) + -15puts 98 + (59872 / (13*8)) * -52

字串 String

puts 'Hello, world!'puts ''puts 'Good-bye.'

puts 'I like ' + 'apple pie.'puts 'You\'re smart!'

puts '12' + 12 #<TypeError: can't convert Fixnum into String>

var1 = 'stop'var2 = 'foobar'var3 = "aAbBcC"

puts var1.reverse # 'pots'puts var2.length # 6puts var3.upcaseputs var3.downcase

Ruby 完全地物件導向# 輸出 "UPPER"puts "upper".upcase

# 輸出 -5 的絕對值puts -5.abs

# 輸出 Fixnum 類別puts 99.class

# 輸出 "Ruby Rocks!" 五次5.times do puts "Ruby Rocks!"end

區域變數 Local Variable

composer = 'Mozart'puts composer + ' was "da bomb", in his day.'

my_composer = 'Beethoven'puts 'But I prefer ' + my_composer + ', personally.'

型別轉換 Conversions

var1 = 2var2 = '5'

puts var1.to_s + var2 # 25puts var1 + var2.to_i # 7

puts 9.to_f / 2 # 4.5

常數 Constant

Foo = 1Foo = 2 # (irb):3: warning: already initialized constant Foo

RUBY_PLATFORM # => "x86_64-darwin10.7.0"ENV # => { "PATH" => "....", "LC_ALL" => "zh_TW.UTF-8" }

空值 nil

nil # nilnil.class # NilClass

nil.nil? # true42.nil? # false

nil == nil # truefalse == nil # false

註解 Comment

# this is a comment line# this is a comment line

=begin This is a comment line This is a comment line=end

陣列 Array

a = [ 1, "cat", 3.14 ]

puts a[0] # 輸出 1puts a.size # 輸出 3

a[2] = nilputs a.inspect # 輸出 [1, "cat", nil]a[99] # nil

colors = ["red", "blue"]

colors.push("black")colors << "white"puts colors.join(", ") # red, blue, black, white

colors.popputs colors.last #black

雜湊 Hash

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

config = { foo: 123, bar: 456 } # 等同於 { :foo => 123, :bar => 456 }

字串符號 Symbols

config = { :foo => 123, :bar => 456 }puts config[:foo] # 輸出 123

"foobar".object_id # 2151854740"foobar".object_id # 2151830100:foobar.object_id # 577768:foobar.object_id # 577768

比較方法puts 1 > 2 # 大於puts 1 < 2 # 小於puts 5 >= 5 # 大於等於puts 5 <= 4 # 小於等於puts 1 == 1 # 等於puts 2 != 1 # 不等於

puts ( 2 > 1 ) && ( 2 > 3 ) # 和puts ( 2 > 1 ) || ( 2 > 3 ) # 或

控制結構 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

三元運算子x = 3if x > 3 y = "foo"else y = "bar"End

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

控制結構 Case

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

迴圈# while 用法範例：i=0while ( i < 10 ) i += 1 next if i % 2 == 0 # 跳過雙數End

# until 用法範例：i = 0i += 1 until i > 10puts i# 輸出 11

# loop 用法範例：i = 0loop do i += 1 break if i > 10 # 中斷迴圈end

真或假 True or False

puts "not execute" if nilputs "not execute" if false

puts "execute" if true # 輸出 executeputs "execute" if “” # 輸出 execute ( 和 JavaScript 不同 )puts "execute" if 0 # 輸出 execute ( 和 C 不同 )puts "execute" if 1 # 輸出 executeputs "execute" if "foo" # 輸出 executeputs "execute" if Array.new # 輸出 execute

方法定義 Methods

def say_hello(name) result = "Hi, " + name return resultend

puts say_hello('ihower')# 輸出 Hi, ihower

def say_hello(name) "Hi, " + nameend

say_hello 'ihower'

? 與 ! 的慣例array=[2,1,3]

array.empty? # falsearray.sort # [1,2,3]

array.inspect # [2,1,3]

array.sort! # [1,2,3]array.inspect # [1,2,3]

類別 Classes

color_string = String.new color_string = "" # 等同

color_array = Array.newcolor_array = [] # 等同

color_hash = Hash.newcolor_hash = {} # 等同

time = Time.new # 內建的時間類別puts time

類別 Classes

class Person # 大寫開頭的常數

def initialize(name) # 建構式 @name = name # 物件變數 end

def say(word) puts "#{word}, #{@name}" # 字串相加 end

end

p1 = Person.new("ihower")p2 = Person.new("ihover")

p1.say("Hello") # 輸出 Hello, ihowerp2.say("Hello") # 輸出 Hello, ihover

方法封裝class MyClass def public_method end private def private_method end protected

def protected_method endend

Class 繼承class Pet attr_accessor :name, :age def say(word) puts "Say: #{word}" endend

class Cat < Pet def say(word) puts "Meow~" super endend

class Dog < Pet def say(word, person) puts "Bark at #{person}!" super(word) endend

Cat.new.say("Hi")Dog.new.say("Hi", "ihower")輸出Meow~Say: HiBark at ihower!Say: Hi

迭代器 Iterator

languages = ['Ruby', 'Javascript', 'Perl']languages.each do |lang| puts "I love #{lang}!"end# I Love Ruby# I Love Javascript# I Love Perl

# 反覆三次3.times do puts 'Good Job!'end# Good Job!# Good Job!# Good Job!

# 從一數到九1.upto(9) { |x| puts x }

# 多一個索引區塊變數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

3.times { puts "Hello" }

迭代器 Iterator

# 迭代並造出另一個陣列a = [ "a", "b", "c", "d" ]b = a.map {|x| x + "!" }puts b.inspect

# 結果是 ["a!", "b!", "c!", "d!"]

# 找出符合條件的值b = [1,2,3].find_all{ |x| x % 2 == 0 }b.inspect# 結果是 [2]

# 迭代並根據條件刪除a = [51, 101, 256]a.delete_if {|x| x >= 100 }# 結果是 [51]

# 客製化排序[2,1,3].sort! { |a, b| b <=> a }# 結果是 [3, 2, 1]

# 計算總和(5..10).inject {|sum, n| sum + n }

# 找出最長字串 find the longest wordlongest = ["cat", "sheep", "bear"].inject do |memo,word| ( memo.length > word.length )? memo : wordend

迭代器 Iterator

file = File.new("testfile", "r")# ... 處理檔案file.close

File.open("testfile", "r") do |file| # ... 處理檔案end# 檔案自動關閉

Yield

# 定義方法def call_block puts "Start" yield yield puts "End"end

call_block { puts "Blocks are cool!" }# 輸出# "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!"}# 輸出# "1: Blocks are cool!"# "2: Blocks are cool!"# "3: Blocks are cool!"