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611 lines
13 KiB
Markdown
611 lines
13 KiB
Markdown
---
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language: ruby
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filename: learnruby-zh.rb
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lang: zh-cn
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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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- ["lidashuang", "https://github.com/lidashuang"]
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- ["ftwbzhao", "https://github.com/ftwbzhao"]
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translators:
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- ["Lin Xiangyu", "https://github.com/oa414"]
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- ["Jiang Haiyun", "https://github.com/haiiiiiyun"]
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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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2**5 #=> 32
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5 % 3 #=> 2
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# 位运算符
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3 & 5 #=> 1
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3 | 5 #=> 7
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3 ^ 5 #=> 6
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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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# 特殊的值也是对象
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nil # 相当于其它语言中的 null
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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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# 不相等运算符
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1 != 1 #=> false
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2 != 1 #=> true
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# 除了false自己，nil是唯一的另一个值为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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# 组合比较运算符
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1 <=> 10 #=> -1
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10 <=> 1 #=> 1
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1 <=> 1 #=> 0
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# 逻辑运算符
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true && false #=> false
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true || false #=> true
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!true #=> false
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# 也有优先级更低的逻辑运算符
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# 它们用于控制流结构中，用来串接语句，直到返回true或false。
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# `do_something_else` 只当 `do_something` 返回true时才会被调用
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do_something() and do_something_else()
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# `log_error` 只当 `do_something` 返回false时才会被调用
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do_something() or log_error()
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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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# 尽可能优先使用单引号的字符串
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# 双引号的字符串会进行一些额外的内部处理
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# 合并字符串，但不能和数字合并
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'hello ' + 'world' #=> "hello world"
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'hello ' + 3 #=> TypeError: can't convert Fixnum into String
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'hello ' + 3.to_s #=> "hello 3"
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# 合并字符串及其运算符
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'hello ' * 3 #=> "hello hello hello "
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# 字符串追加
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'hello' << ' world' #=> "hello world"
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# 打印输出，并在末尾加换行符
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puts "I'm printing!"
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#=> I'm printing!
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#=> nil
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# 打印输出，不加换行符
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print "I'm printing!"
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#=> I'm printing! => nil
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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，使用类似snake_case风格的变量名
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snake_case = true
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# 使用有意义的变量名
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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，内部用整数值表示的可重用的常数
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# 通常用它代替字符串来有效地表示有意义的值
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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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array = [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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[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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# 也只是语法糖
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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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array.last #=> 5
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# 同时指定开始的位置和长度
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array[2, 3] #=> [3, 4, 5]
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# 将数组逆序
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a=[1,2,3]
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a.reverse! #=> [3,2,1]
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# 或者指定一个区间
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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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# 或者像这样
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array.push(6) #=> [1, 2, 3, 4, 5, 6]
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# 检查元素是否包含在数组中
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array.include?(1) #=> true
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# 哈希表是 Ruby 的主要键/值对表示法
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# 哈希表由大括号表示
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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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# 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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# 它们共享一些有用的方法，比如each,map,count等等
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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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# 但是，没有人用for循环。
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# 你应该使用"each"方法，然后再传给它一个块。
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# 所谓块就是可以传给像"each"这样的方法的代码段。
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# 它类似于其它语言中的lambdas, 匿名函数或闭包。
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#
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# 区间上的"each"方法会对区间中的每个元素运行一次块代码。
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# 我们将counter作为一个参数传给了块。
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# 调用带有块的"each"方法看起来如下：
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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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# 你也可以将块包含在一个大括号中：
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(1..5).each { |counter| puts "iteration #{counter}" }
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# 数据结构中的内容也可以使用each来遍历。
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array.each do |element|
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puts "#{element} is part of the array"
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end
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hash.each do |key, value|
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puts "#{key} is #{value}"
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end
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# 如果你还需要索引值，可以使用"each_with_index"，并且定义
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# 一个索引变量
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array.each_with_index do |element, index|
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puts "#{element} is number #{index} in the array"
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end
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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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# Ruby 中还有很多有用的循环遍历函数，
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# 如"map","reduce","inject"等等。
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# 以map为例，它会遍历数组，并根据你在
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# 块中定义的逻辑对它进行处理，然后返回
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# 一个全新的数组。
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array = [1,2,3,4,5]
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doubled = array.map do |element|
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element * 2
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end
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puts doubled
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#=> [2,4,6,8,10]
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puts array
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#=> [1,2,3,4,5]
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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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#=> "Better luck next time"
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# case也可以用区间
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grade = 82
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case grade
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when 90..100
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puts 'Hooray!'
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when 80...90
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puts 'OK job'
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else
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puts 'You failed!'
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end
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#=> "OK job"
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# 异常处理：
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begin
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# 这里的代码可能会抛出异常
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raise NoMemoryError, 'You ran out of memory.'
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rescue NoMemoryError => exception_variable
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puts 'NoMemoryError was raised', exception_variable
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rescue RuntimeError => other_exception_variable
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puts 'RuntimeError was raised now'
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else
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puts 'This runs if no exceptions were thrown at all'
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ensure
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puts 'This code always runs no matter what'
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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 (以及所有的块) 隐式地返回最后语句的值
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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，可选的块参数
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# 可以用 'yield' 关键字调用
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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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# 可以向函数传递一个块
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# "&"标记传递的块是一个引用
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def guests(&block)
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block.call 'some_argument'
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end
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# 可以传递多个参数，这些参数会转成一个数组，
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# 这也是使用星号符 ("*") 的原因：
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def guests(*array)
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array.each { |guest| puts guest }
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end
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# 如果函数返回一个数组，在赋值时可以进行拆分：
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def foods
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['pancake', 'sandwich', 'quesadilla']
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end
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breakfast, lunch, dinner = foods
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breakfast #=> 'pancake'
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dinner #=> 'quesadilla'
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# 按照惯例，所有返回布尔值的方法都以?结尾
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5.even? # false
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5.odd? # true
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# 如果方法名末尾有!，表示会做一些破坏性的操作，比如修改调用者自身。
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# 很多方法都会有一个!的版本来进行修改，和一个非!的版本
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# 只用来返回更新了的结果
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company_name = "Dunder Mifflin"
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company_name.upcase #=> "DUNDER MIFFLIN"
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company_name #=> "Dunder Mifflin"
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company_name.upcase! # we're mutating company_name this time!
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company_name #=> "DUNDER MIFFLIN"
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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，它被这个类的所有实例变量共享
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@@species = "H. sapiens"
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# 基本构造函数
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def initialize(name, age = 0)
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# 将参数值赋给实例变量"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的默认值
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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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# 以上的功能也可以用下面的attr_accessor来封装
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attr_accessor :name
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# Getter/setter方法也可以像这样单独创建
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attr_reader :name
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attr_writer :name
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# 类方法通过使用self与实例方法区别开来。
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# 它只能通过类来调用，不能通过实例调用。
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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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# 初始化一个类
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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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# 调用类方法
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Human.say('Hi') #=> "Hi"
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# 变量的作用域由它们的名字格式定义
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# 以$开头的变量具有全局域
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$var = "I'm a global var"
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defined? $var #=> "global-variable"
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# 以@开头的变量具有实例作用域
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@var = "I'm an instance var"
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defined? @var #=> "instance-variable"
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# 以@@开头的变量具有类作用域
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@@var = "I'm a class var"
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defined? @@var #=> "class variable"
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# 以大写字母开头的变量是常数
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Var = "I'm a constant"
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defined? Var #=> "constant"
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# 类也是对象。因此类也可以有实例变量。
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# 类变量在类以及其继承者之间共享。
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# 基类
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class Human
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@@foo = 0
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def self.foo
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@@foo
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end
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def self.foo=(value)
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@@foo = value
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end
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end
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# 派生类
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class Worker < Human
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end
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Human.foo # 0
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Worker.foo # 0
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Human.foo = 2 # 2
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Worker.foo # 2
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# 类实例变量不能在继承类间共享。
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class Human
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@bar = 0
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def self.bar
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@bar
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end
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def self.bar=(value)
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@bar = value
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end
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end
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class Doctor < Human
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end
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Human.bar # 0
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||
Doctor.bar # nil
|
||
|
||
module ModuleExample
|
||
def foo
|
||
'foo'
|
||
end
|
||
end
|
||
|
||
# '包含'模块后，模块的方法会绑定为类的实例方法
|
||
# '扩展'模块后，模块的方法会绑定为类方法
|
||
|
||
class Person
|
||
include ModuleExample
|
||
end
|
||
|
||
class Book
|
||
extend ModuleExample
|
||
end
|
||
|
||
Person.foo # => NoMethodError: undefined method `foo' for Person:Class
|
||
Person.new.foo # => 'foo'
|
||
Book.foo # => 'foo'
|
||
Book.new.foo # => NoMethodError: undefined method `foo'
|
||
|
||
# 当包含或扩展一个模块时，相应的回调代码会被执行。
|
||
|
||
module ConcernExample
|
||
def self.included(base)
|
||
base.extend(ClassMethods)
|
||
base.send(:include, InstanceMethods)
|
||
end
|
||
|
||
module ClassMethods
|
||
def bar
|
||
'bar'
|
||
end
|
||
end
|
||
|
||
module InstanceMethods
|
||
def qux
|
||
'qux'
|
||
end
|
||
end
|
||
end
|
||
|
||
class Something
|
||
include ConcernExample
|
||
end
|
||
|
||
Something.bar # => 'bar'
|
||
Something.qux # => NoMethodError: undefined method `qux'
|
||
Something.new.bar # => NoMethodError: undefined method `bar'
|
||
Something.new.qux # => 'qux'
|
||
```
|
||
|
||
|
||
## 其它资源
|
||
|
||
- [Learn Ruby by Example with Challenges](http://www.learneroo.com/modules/61/nodes/338) - A variant of this reference with in-browser challenges.
|
||
- [An Interactive Tutorial for Ruby](https://rubymonk.com/) - Learn Ruby through a series of interactive tutorials.
|
||
- [Official Documentation](http://ruby-doc.org/core)
|
||
- [Ruby from other languages](https://www.ruby-lang.org/en/documentation/ruby-from-other-languages/)
|
||
- [Programming Ruby](http://www.amazon.com/Programming-Ruby-1-9-2-0-Programmers/dp/1937785491/) - An older [free edition](http://ruby-doc.com/docs/ProgrammingRuby/) is available online.
|
||
- [Ruby Style Guide](https://github.com/bbatsov/ruby-style-guide) - A community-driven Ruby coding style guide.
|
||
- [Try Ruby](http://tryruby.org) - Learn the basic of Ruby programming language, interactive in the browser.
|