ActiveModel 序列化器：has_many 在运行时有条件？

Question

我使用 rails (5.0.1) 和 active_model_serializers (0.10.2)。我想以某种方式有条件地序列化has_many 关联：

class Question < ApplicationRecord
    has_many :responses, :inverse_of => :question
end

class Response < ApplicationRecord
    belongs_to :question, :inverse_of => :responses
end

class QuestionSerializer < ActiveModel::Serializer
  attributes :id, :title, :created_at, :updated_at
  has_many :responses
end

class ResponseSerializer < ActiveModel::Serializer
  attributes :id, :title
end

我使用 jsonapi 并查询 http://localhost:3000/api/questions/1 我得到这个回复：

Response-1：

{
  "data": {
    "id": "1",
    "type": "questions",
    "attributes": {
      "title": "First",
      "created-at": "2017-02-14T09:49:20.148Z",
      "updated-at": "2017-02-14T13:55:37.365Z"
    },
    "relationships": {
      "responses": {
        "data": [
          {
            "id": "1",
            "type": "responses"
          }
        ]
      }
    }
  }
}

如果我从QuestionSerializer 中删除has_many :responses，我会得到：

响应 2：

{
  "data": {
    "id": "1",
    "type": "questions",
    "attributes": {
      "title": "First",
      "created-at": "2017-02-14T09:49:20.148Z",
      "updated-at": "2017-02-14T13:55:37.365Z"
    }
  }
}

我如何有条件地在运行时获得 Response-1 或 Response-2？我尝试了所有找到的建议 - 都不适用于 AMS 0.10.2。目前，该条件仅以这种方式起作用：

class QuestionSerializer < ActiveModel::Serializer
  attributes :id, :title, :created_at, :updated_at
  has_many :responses if true
end

或者：

class QuestionSerializer < ActiveModel::Serializer
  attributes :id, :title, :created_at, :updated_at
  has_many :responses if false
end

在这两种情况下，我确实得到了 Response-1 或 Response-2。但这是硬编码的，我想可能将参数传递给序列化程序或做一些类似的事情。

我该怎么办？

Answer 1

我认为您已经回答了自己的问题。如果您查看 AMS documentation for associations，它会说支持条件。

据我所知，你只是一个错字

class QuestionSerializer < ActiveModel::Serializer
   has_many :responses, if: false
end

attributes 方法还支持if 选项，如here 所述。

你的active_model_serializers 是什么版本？

编辑： 我的回答也有错误。我正在使用active_model_serializers (0.10.3)，我可以做到

class QuestionSerializer < ActiveModel::Serializer
   has_many :responses, if: -> { false }
end

if 选项适用于方法、过程或字符串。我认为您可以在运行时通过提供一个方法作为条件来决定。

class QuestionSerializer < ActiveModel::Serializer
  attr_writer :should_render_association
  has_many :responses, if: -> { should_render_association }
end
# Usage: 
serializer = QuestionSerializer.new(question)
serializer.should_render_association = false
serializer.to_json
# => no "responses" key

Answer 2

感谢@gkats，我找到了答案（AMS 0.10.2）：

class QuestionSerializer < ActiveModel::Serializer
  attributes :id, :title, :created_at, :updated_at
  has_many :responses, if: -> { should_render_association }

  def should_render_association
    @instance_options[:show_children]
  end
end

class Api::ResponsesController < Api::ApplicationController
  def show
    render json: @response, show_children: param[:include_children]
  end
end

问题在于语法：序列化程序中的if: 应该应用于块而不是函数。

Answer 3

我在同样的问题上苦苦挣扎。这是我想出的可行解决方案。

使用except: [:key_one, :key_two] 作为参数进行初始化。

class QuestionsController
    def index
        @questions = Question.all
        render(json: ActiveModel::ArraySerializer.new(@questions,
                                                      each_serializer: QuestionSerializer,
                                                      root: 'questions',
                                                      except: [:responses])
        )
    end

    def show 
        # you can also pass the :except arguments here
        # render(json: QuestionSerializer.new(@question, except: [:responses]).to_json)
        render(json: QuestionSerializer.new(@question).to_json)
    end
end

https://www.rubydoc.info/gems/active_model_serializers/0.9.3/ActiveModel%2FArraySerializer:initialize

https://www.rubydoc.info/gems/active_model_serializers/0.9.1/ActiveModel%2FSerializer:initialize

Answer 4

您可以通过以下方式从父序列化程序传递参数，并在子序列化程序中根据这些参数显示或隐藏属性。

父序列化器：

class LocationSharesSerializer < ActiveModel::Serializer
  attributes :id, :locations, :show_title, :show_address
     
  def locations
    ActiveModelSerializers::SerializableResource.new(object.locations, {
      each_serializer: PublicLocationSerializer,
      params: { 
        show_title: object.show_title
      },
    })
  end

end

子序列化程序

class PublicLocationSerializer < ActiveModel::Serializer
  attributes :id, :latitude, :longitude, :title, :directions, :description, :address, :tags, :created_at, :updated_at, :photos

  def title
    object.title if @instance_options[:params][:show_title]
  end

end