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Adam Bard
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zh-cn/ruby-cn.html.markdown
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---
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language: ruby
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filename: learnruby.rb
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contributors:
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- ["David Underwood", "http://theflyingdeveloper.com"]
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- ["Joel Walden", "http://joelwalden.net"]
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- ["Luke Holder", "http://twitter.com/lukeholder"]
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translators:
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- ["Lin Xiangyu", "https://github.com/oa414"]
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---
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```ruby
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# 这是单行注释
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=begin
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这是多行注释
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没人用这个
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你也不该用
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=end
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# 首先，也是最重要的，所有东西都是对象
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# 数字是对象
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3.class #=> Fixnum
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3.to_s #=> "3"
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# 一些基本的算术符号
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1 + 1 #=> 2
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8 - 1 #=> 7
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10 * 2 #=> 20
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35 / 5 #=> 7
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# 算术符号只是语法糖而已
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# 实际上是调用对象的方法
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1.+(3) #=> 4
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10.* 5 #=> 50
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# 特殊的只也是对象
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nil # 空
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true # 真
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false # 假
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nil.class #=> NilClass
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true.class #=> TrueClass
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false.class #=> FalseClass
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# 相等运算符
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1 == 1 #=> true
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2 == 1 #=> false
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# 不等运算符
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1 != 1 #=> false
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2 != 1 #=> true
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!true #=> false
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!false #=> true
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# 除了false自己，nil是唯一的值为false的对象
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!nil #=> true
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!false #=> true
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!0 #=> false
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# 更多比较
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1 < 10 #=> true
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1 > 10 #=> false
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2 <= 2 #=> true
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2 >= 2 #=> true
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# 字符串是对象
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'I am a string'.class #=> String
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"I am a string too".class #=> String
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placeholder = "use string interpolation"
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"I can #{placeholder} when using double quoted strings"
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#=> "I can use string interpolation when using double quoted strings"
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# 输出值
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puts "I'm printing!"
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# 变量
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x = 25 #=> 25
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x #=> 25
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# 注意赋值语句返回了赋的值
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# 这意味着你可以用多重赋值语句
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x = y = 10 #=> 10
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x #=> 10
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y #=> 10
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# 按照惯例，用snake_case 作为变量名
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snake_case = true
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# 使用具有描述性的运算符
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path_to_project_root = '/good/name/'
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path = '/bad/name/'
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# 符号（Symbols，也是对象)
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# 符号是不可变的，内部用整数类型表示的可重用的值。通常用它代替字符串来有效地表达有意义的值
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:pending.class #=> Symbol
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status = :pending
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status == :pending #=> true
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status == 'pending' #=> false
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status == :approved #=> false
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# 数组
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# 这是一个数组
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[1, 2, 3, 4, 5] #=> [1, 2, 3, 4, 5]
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# 数组可以包含不同类型的元素
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array = [1, "hello", false] #=> => [1, "hello", false]
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# 数组可以被索引
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# 从前面开始
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array[0] #=> 1
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array[12] #=> nil
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# 像运算符一样，[var]形式的访问
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# 也就是一个语法糖
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# 实际上是调用对象的[] 方法
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array.[] 0 #=> 1
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array.[] 12 #=> nil
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# 从尾部开始
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array[-1] #=> 5
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# 同时指定开始的位置和结束的位置
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array[2, 4] #=> [3, 4, 5]
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# 或者指定一个范围
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array[1..3] #=> [2, 3, 4]
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# 像这样往数组增加一个元素
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array << 6 #=> [1, 2, 3, 4, 5, 6]
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# 哈希表是Ruby的键值对的基本数据结构
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# 哈希表由大括号定义
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hash = {'color' => 'green', 'number' => 5}
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hash.keys #=> ['color', 'number']
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# 哈希表可以通过键快速地查询
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hash['color'] #=> 'green'
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hash['number'] #=> 5
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# 查询一个不存在地键将会返回nil
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hash['nothing here'] #=> nil
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# 用 #each 方法来枚举哈希表:
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hash.each do |k, v|
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puts "#{k} is #{v}"
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end
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# 从Ruby 1.9开始, 用符号作为键的时候有特别的记号表示:
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new_hash = { defcon: 3, action: true}
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new_hash.keys #=> [:defcon, :action]
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# 小贴士：数组和哈希表都是可枚举的
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# 它们可以共享一些有用的方法，比如each, map, count, 和more
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# 控制流
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if true
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"if statement"
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elsif false
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"else if, optional"
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else
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"else, also optional"
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end
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for counter in 1..5
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puts "iteration #{counter}"
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end
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#=> iteration 1
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#=> iteration 2
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#=> iteration 3
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#=> iteration 4
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#=> iteration 5
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# 然而
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# 没人用for循环
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# 用`each`来代替，就像这样
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(1..5).each do |counter|
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puts "iteration #{counter}"
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end
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#=> iteration 1
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#=> iteration 2
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#=> iteration 3
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#=> iteration 4
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#=> iteration 5
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counter = 1
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while counter <= 5 do
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puts "iteration #{counter}"
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counter += 1
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end
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#=> iteration 1
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#=> iteration 2
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#=> iteration 3
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#=> iteration 4
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#=> iteration 5
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grade = 'B'
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case grade
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when 'A'
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puts "Way to go kiddo"
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when 'B'
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puts "Better luck next time"
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when 'C'
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puts "You can do better"
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when 'D'
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puts "Scraping through"
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when 'F'
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puts "You failed!"
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else
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puts "Alternative grading system, eh?"
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end
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# 函数
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def double(x)
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x * 2
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end
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# 函数 (以及所有的方法块) 隐式地返回了最后语句的值
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double(2) #=> 4
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# 当不存在歧义的时候括号是可有可无的
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double 3 #=> 6
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double double 3 #=> 12
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def sum(x,y)
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x + y
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end
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# 方法的参数通过逗号分隔
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sum 3, 4 #=> 7
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sum sum(3,4), 5 #=> 12
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# yield
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# 所有的方法都有一个隐式的块参数
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# 可以用yield参数调用
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def surround
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puts "{"
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yield
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puts "}"
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end
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surround { puts 'hello world' }
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# {
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# hello world
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# }
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# 用class关键字定义一个类
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class Human
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# 一个类变量，它被这个类地所有实例变量共享
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@@species = "H. sapiens"
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# 构造函数
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def initialize(name, age=0)
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# 将参数name的值赋给实例变量@name
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@name = name
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# 如果没有给出age, 那么会采用参数列表中地默认地值
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@age = age
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end
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# 基本的 setter 方法
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def name=(name)
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@name = name
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end
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# 基本地 getter 方法
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def name
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@name
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end
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# 一个类方法以self.开头
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# 它可以被类调用，但不能被类的实例调用
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def self.say(msg)
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puts "#{msg}"
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end
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def species
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@@species
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end
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end
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# 类的例子
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jim = Human.new("Jim Halpert")
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dwight = Human.new("Dwight K. Schrute")
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# 让我们来调用一些方法
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jim.species #=> "H. sapiens"
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jim.name #=> "Jim Halpert"
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jim.name = "Jim Halpert II" #=> "Jim Halpert II"
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jim.name #=> "Jim Halpert II"
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dwight.species #=> "H. sapiens"
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dwight.name #=> "Dwight K. Schrute"
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# 调用对象的方法
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Human.say("Hi") #=> "Hi"
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```
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