如何从活动模型序列化中的关联模型中提取数据？答案

【问题标题】：How to pull data from associative models in active model serializes?如何从活动模型序列化中的关联模型中提取数据？
【发布时间】：2018-05-26 08:24:30
【问题描述】：

我使用active_model_serializers gem 以JSON 发送响应。我从关联模型中提取数据，但是如何仅从 questions 表中获取那些数据，其中 UserType 等于 clients.UserType。

ClientSerializer:

class ClientSerializer < ActiveModel::Serializer
  attributes :id, :username, :access_token, :UserType

  has_many :questions, include: :all
end

和QuestionSerializer:

class QuestionSerializer < ActiveModel::Serializer
  attributes :id, :question, :client_id, :UserType
  belongs_to :user
end

这是JSON的输出：

{
    "id": 4,
    "username": "171fdkjgku",
    "access_token": "77NVccAJG7hEKSGQUcKkSip5",
    "UserType": 1,
    "questions": [
        {
            "id": 1,
            "question": "Lorem Ipsum",
            "client_id": 4,
            "UserType": 1
        },
        {
            "id": 2,
            "question": "Lorem Ipsum 2",
            "client_id": 4,
            "UserType": 0
        },
        {
            "id": 3,
            "question": "Lorem Ipsum 3",
            "client_id": 4,
            "UserType": 1
        }
    ]
}

预期输出JSON:

{
    "id": 4,
    "username": "171fdkjgku",
    "access_token": "77NVccAJG7hEKSGQUcKkSip5",
    "UserType": 1,
    "questions": [
        {
            "id": 1,
            "question": "Lorem Ipsum",
            "client_id": 4,
            "UserType": 1
        },
        {
            "id": 3,
            "question": "Lorem Ipsum 3",
            "client_id": 4,
            "UserType": 1
        }
    ]
}

【问题讨论】：

标签： ruby-on-rails associations active-model-serializers

【解决方案1】：

您可以通过自己定义questions 方法并在其中获取范围问题来实现此目的：

class ClientSerializer < ActiveModel::Serializer
  attributes :id, :username, :access_token, :UserType, :questions

  def questions
    ques = self.object.questions.where(UserType: self.object.UserType).to_a
    ActiveModel::ArraySerializer.new(ques, each_serializer: QuestionSerializer).as_json
  end
end

【讨论】：