使用多个模块扩展的对象中方法的Ruby优先级 [英] Ruby precedence of methods in objects extended with multiple modules

问题描述

给出以下内容:

class User; attr_accessor :roles; end

module RegisteredUser
  def default_context
    Submission
  end
end

module Admin
  def default_context
    Review
  end
end

current_user = User.new
current_user.roles = ["registered_user", "admin"]
current_user.roles.each do |role|
  role_module = role.gsub(/ /, '_').camelize
  if module_exists?(role_module)
    current_user.extend role_module.constantize
  end
end
context = self.extend current_user.default_context

是否可以设置User#default_context的优先级?也就是说，无论current_user的扩展顺序如何，Admin#default_context始终优先于RegisteredUser#default_context?

Is there a way to set the priority of User#default_context? That is, can I say that the Admin#default_context always takes priority over RegisteredUser#default_context regardless of the order in which current_user is extended?

推荐答案

method_added在Module中.

我的意思实际上是included，而不是extended，但是两者都在Module中.

I actually meant included, not extended, but both are also in Module.

该机制将围绕执行以下操作:

The mechanism would revolve around doing something like this:

module Foo
  def self.included(base)
    base.extend(FooMethods)
  end

  module FooMethods
    def bar
      # Whatever
    end
  end
end

在Foo.included内部，您可以根据任意标准确定是否应将相关方法添加到base(包括模块的实体)中.

Inside Foo.included you can determine, based on arbitrary criteria, whether or not the methods in question should be added to base (the entity including the module).

在您的情况下，您可以检查是否已包含更高优先级"模块，或者查看模块是否是更高优先级"模块.基于此，您将决定是否添加方法.

In your case, you could check to see if a "higher priority" module was already included, or see if the module is the "higher priority" module. Based on that you'd decide whether or not to add the methods.

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