Ruby：在模块中调用类方法

Question

I have a module, whose purpose is to act on any given ActiveRecord instance.

For argument's sake, let's say that this method puts the string "match" if it matches certain properties with another instance of the same type.

module Foo
  def check_against_other_instances
    self.all.each do |instance|
      if self.respond_to? :color && self.color == instance.color
        puts "match"
      end
    end
  end
end

However, I can't just simply call self.all here, because self is an instance. How do I call the class method all from here?

Answer 1

啊..我问后几乎就找到了解决方案...

self.class.all.each do |instance| ...

Answer 2

if you want to extend the behavior of rails classes, then you are best of using ActiveSupport::Concern!

http://apidock.com/rails/ActiveSupport/Concern

Answer 3

You can pull the name of a class from an instance and then constantize it.

For example, given a class Thing :

t = Thing.new
t.class.name
  # => "Thing"
t.class.name.constantize
  # => Thing