ruby – 如何检测递归数组和散列？

这是一个不错的方式,迭代所有内容并保持您看到的对象的哈希值(用于快速查找)

class Object
  def is_recursive?(known = {})
    false
  end
end

module Enumerable
  def is_recursive?(known = {})
    return true if known.include?(self)
    known[self] = true
    begin
      any? do |*args|
        args.any?{|item| item.is_recursive?(known)}
      end
    ensure
      known[self] = false
    end
  end
end

x = []; x << x
p x.is_recursive? # => true
p ({x => 42}).is_recursive? # => true
p [{foo: x}].is_recursive? # => true
p [[[[[[:foo],{Bar: [42]}]]]]].is_recursive? # => false

请注意,这有点粗糙,你可能遇到麻烦.例如,你有[1..Float :: INFINITY] .is_recursive？的无限循环,虽然这很容易用

class Range
  def is_recursive?(known = {})
    false # optimization
  end
end