关于 Ruby 有多少解构赋值 / pattern matching 这件事。

• 基础

  a, b = [1, 2]
  # a = 1 ; b = 2

• 复杂的基础

  a, (b, c), d = [1, [2, 3], 4]
  # a = 1 ; b = 2 ; c = 3 ; d = 4

• 解构数组

  a, *b = [1, 2, 3, 4]
  # a = 1 ; b = [2, 3, 4]

• in 关键字

  [1, 2, 3] in a, b, c
  # a = 1 ; b = 2 ; c = 3

• =>

  [1, 2, 3] => a, b, c
  # a = 1 ; b = 2 ; c = 3

  似乎只有右边放变量才能解构哈希

  {a: 1, b: 2} => a:, b:
  # a = 1 ; b = 2

• 更奇怪的解构

  通过类型来解构

  [1,2,3,"str",4,5,6] => *a, String => b, *c
  # a = [1, 2, 3] ; b = "str" ; c = [4, 5, 6]

  通过值来解构

  [1,2,3,"str",4,5,6] => *a, 4 => b, *c
  # a = [1, 2, 3, "str"] ; b = 4 ; c = [5, 6]

  但是类型不能是值……？

  [1,2,3,String,4,5,6] => *a, String => b, *c
  #  [1, 2, 3, String, 4, 5, 6] does not match to find pattern (NoMatchingPatternError)

• 还能类似 Elixir 那样 pin 一个值

  b = 3
  [1, 2, 3, 4, 5] => *a, ^b, *c
  # a = [1, 2] ; b = 3 ; c = [4, 5]

• 也能自定义解构规则

  class Test
      def deconstruct_keys(keys)
          p keys
          keys.each_with_object({}) do |key, hash|
          hash[key] = rand
          end
      end
      def deconstruct
          [1,1,4,5,1,4]
      end
  end
  
  t = Test.new
  t => a, b, c, d, e, f
  # a = 1 ; b = 1 ; c = 4 ; d = 5 ; e = 1 ; f = 4
  t => a:, b:, c:
  # a, b, c 为随机数