Question

亲爱的，我有一个Student模型，我在其中指定了一些name_scope，例如from_program，from_year，from_school，has_status，from_course等......

无论如何，我可以在运行时根据某些标准动态地将不同的named_scope链接在一起吗？

例如，如果访问数据的用户来自财务部门，我希望能够仅将from_school和has_status链接在一起。如果用户是讲师，我希望能够将from_course，from_school链接在一起，等等......

我应该使用named_scope吗？或者我应该回到指定条件的旧方法？

提前感谢您的建议！ =）顺便说一句，我正在使用rails 2.3

Answer 1

我不确定，如果我理解，但我认为你可以这样做：

class Student

  named_scope from_program, lambda{|program| :conditions => {:program => program}}
  named_scope from_year, lambda{|year| :conditions => {:year => year}}
  named_scope has_status, lambda{|status| :conditions => {:status => status}}

  def self.from_finance(school, status)
    self.from_school(school).has_status(status)
  end

end

或更一般

def self.get_students(params)
  scope = self
  [:program, :year, :school, :course].each do |s|
    scope = scope.send("from_#{s}", params[s]) if params[s].present?
  end
  scope = scope.has_status(params[:status]) if params[:status].present?
  scope
end

Answer 2

您可以尝试这样的事情

  Class User extend ActiveRecord::Base
  belongs_to :semester

  named_scope :year, lambda { |*year|
    if year.empty? || year.first.nil?
      { :joins => :semester, :conditions => ["year = #{CURRENT_SEMESTER}"]}
    else
      { :joins => :semester, :conditions => ["year = #{year}"]}
    end
    }

  end

你可以像这样打电话

  User.year     # defaults to CURRENT_SEMESTER constant
  User.year()  # same as above
  User.year(nil)  # same as above; useful if passing a param value that may or may not exist, ie, param[:year]
  User.year(2010)

以同样的方式传递参数

动态`named_scope`取决于某些标准

2 个答案: