如何在Rails 3.1中复制class_inheritable_accessor的行为？ [英] How do I replicate class_inheritable_accessor's behavior in Rails 3.1?

问题描述

从Rails 3.1开始， class_inheritable_accessor 产生弃用警告，告诉我改为使用 class_attribute 。但是 class_attribute 的行为方式与我将演示的重要方式不同。

Beginning with Rails 3.1, class_inheritable_accessor produces deprecation warnings, telling me to use class_attribute instead. But class_attribute behaves differently in an important way which I will demonstrate.

class_inheritable_attribute 将是一个演示者类，如下所示：

A typical use of class_inheritable_attribute would be a presenter class, like so:

module Presenter
  class Base
    class_inheritable_accessor :presented
    self.presented = {}

    def self.presents(*types)
      types_and_classes = types.extract_options!
      types.each {|t| types_and_classes[t] = t.to_s.tableize.classify.constantize }
      attr_accessor *types_and_classes.keys
      types_and_classes.keys.each do |t|
        presented[t] = types_and_classes[t]
      end
    end
  end
end

class PresenterTest < Presenter::Base
  presents :user, :person
end

Presenter::Base.presented => {}
PresenterTest.presented => {:user => User, :person => Person}

但是使用 class_attribute ，子类将污染他们的父母：

But using class_attribute, subclasses will pollute their parents:

Presenter::Base => {:user => User, :person => Person}

这根本不是所希望的行为。是否有其他类型的访问器行为正确，或者我是否需要完全切换到另一种模式？如果没有 class_inheritable_accessor ，我应该如何复制相同的行为？

Which is not desired behavior at all. Is there another type of accessor that behaves the correct way, or do I need to switch to another pattern altogether? How should I replicate the same behavior without class_inheritable_accessor?

推荐答案

class_attribute 如果按预期使用，则不会污染其父级。确保你没有就地改变可变项。

class_attribute won't pollute its parent if it's used as intended. Make sure you're not changing the mutable items in-place.

types_and_classes.keys.each do |t|
  self.presented = presented.merge({t => types_and_classes[t]})
end

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