Ruby：is_a？ instance_of？在基本对象中

Question

如何is_a？ instance_of？方法与 BasicObject 的子类一起使用 ?

class My < BasicObject
  DELEGATE = [:is_a?, :instance_of?]
  def method_missing(name, *args, &blk)
    superclass unless DELEGATE.include? name
    ::Kernel.send(name,*args, &blk) 
  end
end

my = My.new
my.is_a? BasicObject  #=> true
my.is_a? My           #=> false ???
my.instance_of? My    #=> false ???

Answer 1

::Kernel.send(name,*args, &blk) 使用参数 args 和块 &blk.[=27 在 class Kernel 上调用方法 name =]

当你运行my.is_a? Myname是:is_a?，*args是My，&blk是nil。你真是运行宁Kernel.is_a? My.

相反，如果您想为 BasicObject 重新实现 is_a?，您可以走 class 的 ancestors...

  def is_a?(target)
    # I don't know how to get the current class from an instance
    # that isn't an Object, so I'm hard coding the class instead.
    return ::My.ancestors.include?(target)
  end

Answer 2

您可以从 Kernel:

窃取 is_a?

class My < BasicObject
  define_method(:is_a?, ::Kernel.method(:is_a?))
end

m = My.new
m.is_a?(My)          #=> true
m.is_a?(BasicObject) #=> true
m.is_a?(Object)      #=> false

如果您要构建自己的对象层次结构，您也可以定义自己的 Kernel，例如：

module MyKernel
  [:is_a?, :instance_of?, :class].each do |m|
    define_method(m, ::Kernel.method(m))
  end
end

class My < BasicObject
  include ::MyKernel
end

Ruby：is_a？ instance_of？在基本对象中

Ruby: is_a? and instance_of? in BasicObject

ruby

introspection

delegation