ruby-on-rails – Rails：lambda,scope和class方法有什么区别？

所有这些都返回相同的结果.

问题：

> Ruby / Rails中有哪些优先使用一种？
>在什么情况下您将使用lambda,scope或class方法(最佳做法).

class Cars < ActiveRecord::Base     
  attr_accessible :manufacturer,:price,:used

  #one
  scope :used_and_cheap_lambda,lambda { where('used = ?',true ).where('price >= ?',30000) }

  #two
  scope :used_and_cheap_scope,where('used = ?',30000)

  #three
  def self.used_and_cheap_class
    where('used = ?',30000)
  end
end





Cars.used_and_cheap_lambda.count
=> #24

Cars.used_and_cheap_class.count
=> #24

Cars.used_and_cheap_scope.count
=> #24