ruby-on-rails - 在 Rails 3 中使用多个可选的 where 条件(子句)进行查询？

Question

在 Rails 3.2 中，如何通过多个可选参数进行搜索/过滤？使用下面的设置，我目前收到以下错误。非常感谢任何帮助。

undefined method `paginate' for nil:NilClass

Application Trace | Framework Trace | Full Trace
app/controllers/contacts_controller.rb:50:in `index'

这是我的 contacts_controller 中的索引操作:

def index
  city = params[:city]
  state = params[:state]
  zip = params[:zip]
  @contacts = Contact.search(city,state,zip).paginate(:page => params[:page], :per_page => items_per_page)
end

这是我的联系人模型中的搜索方法:

def self.search(city, state, zip)
  joins(:profile => :addresses)
  .where("city like ?", "%#{city}%") unless city.blank?
  .where("state = ?", state) unless state.blank?
  .where("zip like ?", "%#{zip}%") unless zip.blank?
end

Answer 1

尝试更明确地返回，例如像那样:

def self.search(city, state, zip)
  query_obj = joins(:profile => :addresses)
  query_obj = query_obj.where("city like ?", "%#{city}%") unless city.blank?
  query_obj = query_obj.where("state = ?", state) unless state.blank?
  query_obj = query_obj.where("zip like ?", "%#{zip}%") unless zip.blank?

  query_obj
end