模型保存时得到 ActiveRecord::AssociationTypeMismatch

Question

我在使用我的 REST API 保存模型时遇到问题。我有一个包含许多任务和一个客户关联的卡片模型：

class Card < ActiveRecord::Base
  belongs_to :customer

  has_many :card_tasks
  has_many :tasks, :through => :card_tasks

  accepts_nested_attributes_for :tasks
  accepts_nested_attributes_for :card_tasks
  accepts_nested_attributes_for :customer

end


class CardTask < ActiveRecord::Base
  belongs_to :task
  belongs_to :card

  accepts_nested_attributes_for :task
  accepts_nested_attributes_for :card
end

class Task < ActiveRecord::Base
    has_many :cards, :through => :card_tasks
    has_many :card_tasks
end

当我发送这样的 json 时：

{
    "card" = > {
        "miscellaneous" = > "Obervations diverses", 
        "heater" = > "0", 
        "water_quality" = > "", 
        "customer" = > {
          "id" = > "2", "house_name" = > "house_name2", "city" = > "city_2", "lastname" = > "lastname2", "sci" = > "sci2", "postal_code" = > "potal_code_2", "address_line_1" = > "address_line_2", "updated_at" = > "2012-03-05 18:20:57 +0000", "created_at" = > "2012-03-05 18:20:54 +0000", "firstname" = > "firstname2", "address_line_2" = > "address_line_3", "water_used" = > "0"
         },
         "tasks" = > [
          {
            "title" = > "Nettoyage ligne eau", "id" = > "6", "updated_at" = > "2012-02-17 08:40:47 +0000", "created_at" = > "2012-02-17 08:40:47 +0000"
          }, 
          {
            "title" = > "Surveillance", "id" = > "4", "updated_at" = > "2012-02-17 08:40:47 +0000", "created_at" = > "2012-02-17 08:40:47 +0000"
          }
         ]
    }
}

我的创建动作：

  def create
      card = Card.new(params[:card])
      if (card.save)
        respond_with({ :card => card} , :location => nil, status: :created) and return
      end
      respond_with({ :errors => card.errors }, :location => nil, status: :unprocessable_entity)  and return
  end

执行此操作时，我得到了一个：

ActiveRecord::AssociationTypeMismatch (Task(#70249431354580) expected, got ActiveSupport::HashWithIndifferentAccess(#70249421573300)):
  app/controllers/cards_controller.rb:14:in `new'
  app/controllers/cards_controller.rb:14:in `create'

我做错了什么？

Answer 1

问题出在 JSON 结构中，Rails 需要 tasks_attributes，而不是 tasks。详情请查看this question。