在Ruby中列出attr_accessors的最快/一线方式？

Question

列出用attr_accessor定义的所有方法的最短，单行方法是什么？我想这样做，如果我有一个类MyBaseClass，任何扩展它的东西，我可以在子类中定义attr_accessor。像这样：

class MyBaseClass < Hash
  def attributes
    # ??
  end
end

class SubClass < MyBaseClass
  attr_accessor :id, :title, :body
end

puts SubClass.new.attributes.inspect #=> [id, title, body]

如何仅显示attr_reader和attr_writer定义？

Answer 1

将属性提取到数组中，将它们分配给constant，然后将splat分配到attr_accessor。

class SubClass < MyBaseClass
  ATTRS = [:id, :title, :body]
  attr_accessor(*ATTRS)
end

现在您可以通过常量访问它们：

puts SubClass.ATTRS #=> [:id, :title, :body]

Answer 2

没有办法（单行或其他方式）列出attr_accessor定义的所有方法，只列出attr_accessor定义的方法，而不定义自己的attr_accessor。

这是一个覆盖MyBaseClass中的attr_accessor的解决方案，用于记住使用attr_accessor创建的方法：

class MyBaseClass
  def self.attr_accessor(*vars)
    @attributes ||= []
    @attributes.concat vars
    super(*vars)
  end

  def self.attributes
    @attributes
  end

  def attributes
    self.class.attributes
  end
end

class SubClass < MyBaseClass
  attr_accessor :id, :title, :body
end

SubClass.new.attributes.inspect #=> [:id, :title, :body]

Answer 3

继承人使用mixin而不是继承：

module TrackAttributes
  def attr_readers
    self.class.instance_variable_get('@attr_readers')
  end

  def attr_writers
    self.class.instance_variable_get('@attr_writers')
  end

  def attr_accessors
    self.class.instance_variable_get('@attr_accessors')
  end

  def self.included(klass)
    klass.send :define_singleton_method, :attr_reader, ->(*params) do
      @attr_readers ||= []
      @attr_readers.concat params
      super(*params)
    end

    klass.send :define_singleton_method, :attr_writer, ->(*params) do
      @attr_writers ||= []
      @attr_writers.concat params
      super(*params)
    end

    klass.send :define_singleton_method, :attr_accessor, ->(*params) do
      @attr_accessors ||= []
      @attr_accessors.concat params
      super(*params)
    end
  end
end

class MyClass
  include TrackAttributes

  attr_accessor :id, :title, :body
end

MyClass.new.attr_accessors #=> [:id, :title, :body]

Answer 4

跟进Christian的回复，但修改为使用ActiveSupport :: Concern ......

module TrackAttributes
  extend ActiveSupport::Concern

  included do
    define_singleton_method(:attr_reader) do |*params|
      @attr_readers ||= []
      @attr_readers.concat params
      super(*params)
    end

    define_singleton_method(:attr_writer) do |*params|
      @attr_writers ||= []
      @attr_writers.concat params
      super(*params)
    end

    define_singleton_method(:attr_accessor) do |*params|
      @attr_accessors ||= []
      @attr_accessors.concat params
      super(*params)
    end
  end

  def attr_readers
    self.class.instance_variable_get('@attr_readers')
  end

  def attr_writers
    self.class.instance_variable_get('@attr_writers')
  end

  def attr_accessors
    self.class.instance_variable_get('@attr_accessors')
  end

end

Answer 5

类定义

class MyBaseClass
  attr_writer :an_attr_writer
  attr_reader :an_attr_reader

  def instance_m
  end

  def self.class_m
  end
end

class SubClass < MyBaseClass
  attr_accessor :id

  def sub_instance_m
  end

  def self.class_sub_m
  end
end

作为类方法调用

p SubClass.instance_methods - Object.methods    
p MyBaseClass.instance_methods - Object.methods

调用实例方法

a = SubClass.new
b = MyBaseClass.new

p a.methods - Object.methods
p b.methods - Object.methods

两者都会输出相同的

#=> [:id, :sub_instance_m, :id=, :an_attr_reader, :instance_m, :an_attr_writer=]
#=> [:an_attr_reader, :instance_m, :an_attr_writer=]

如何判断哪个是作家读者和访问者？

attr_accessor既是attr_writer又是attr_reader

attr_reader在方法名称

之后输出no =

attr_writer在方法名称

之后输出=

您始终可以使用正则表达式来过滤该输出。

Answer 6

可以使用等号匹配逻辑对其进行过滤：

X (T r t) b