Question

我们知道，方法Module#refine是Module类中的私有实例方法：

% Module.private_instance_methods(false)
[:remove_const, :method_added, :append_features, :method_removed, 
:method_undefined, :extend_object, :prepend_features, :using, :refine, 
:initialize, :initialize_copy, :initialize_clone, :public, :protected, 
:module_function, :private, :included, :extended, :prepended]

这意味着Object类本身可以使用refine或Object#send调用BasicObject#__send__方法，因为Object.singleton_class.ancestors.include?(Module)为真。

但执行undefined method时会出现实际Object.refine错误：

# ./tmp/mytest.rb
Module.private_instance_methods(false).map do |m|
  begin
    p [m, Object.singleton_class.instance_method(m)]
  rescue StandardError => e
    p [m, e.exception]
  end
end

输出就是这个。 refine方法位于中间。

% ruby -v
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-darwin17]
% ruby ./tmp/mytest.rb
[:remove_const, #<UnboundMethod: #<Class:Object>#remove_const>]
[:method_added, #<UnboundMethod: #<Class:Object>#method_added>]
[:append_features, #<NameError: undefined method `append_features' for class `#<Class:Object>'>]
[:method_removed, #<UnboundMethod: #<Class:Object>#method_removed>]
[:method_undefined, #<UnboundMethod: #<Class:Object>#method_undefined>]
[:extend_object, #<NameError: undefined method `extend_object' for class `#<Class:Object>'>]
[:prepend_features, #<NameError: undefined method `prepend_features' for class `#<Class:Object>'>]
[:using, #<UnboundMethod: #<Class:Object>#using>]
[:refine, #<NameError: undefined method `refine' for class `#<Class:Object>'>]
[:initialize, #<UnboundMethod: #<Class:Object>#initialize>]
[:initialize_copy, #<UnboundMethod: #<Class:Object>#initialize_copy>]
[:initialize_clone, #<UnboundMethod: #<Class:Object>#initialize_clone>]
[:public, #<UnboundMethod: #<Class:Object>#public>]
[:protected, #<UnboundMethod: #<Class:Object>#protected>]
[:module_function, #<NameError: undefined method `module_function' for class `#<Class:Object>'>]
[:private, #<UnboundMethod: #<Class:Object>#private>]
[:included, #<UnboundMethod: #<Class:Object>#included>]
[:extended, #<UnboundMethod: #<Class:Object>#extended>]
[:prepended, #<UnboundMethod: #<Class:Object>#prepended>]

在上面的结果中，refine方法除外，append_features，prepend_features，extend_object和module_function方法提升NameError，而其他方法成功查找方法。

看起来好奇，我想知道会发生什么。

Answer 1

经过检查，operator delete(p)似乎是:refine，但我在UnboundMethod周围发现了这一点。从pry控制台：

pry

您会注意到：

Module.private_instance_methods(:false)

[ 76] refine(arg1) Module (unbound) NameError代码示例中出现了{{1}}

为什么表达式`Object.singleton_class.instance_method（：refine）`引发`NameError`？

1 个答案: