活動模型序列化器-自定義響應

Question

我正在嘗試為以下項自定義序列化器：

# in DB
{
  "id": 1,
  "measurement": 10.5,
  "sequence": 1,
  "time_stamp": "2016-05-25T04:53:38.000Z",
  "device_id": 2,
  "patient_id": 3,
  "measurement_type": "ecg"
},
{
  "id": 2,
  "measurement": 20.5,
  "sequence": 2,
  "time_stamp": "2016-05-25T04:53:38.000Z",
  "device_id": 2,
  "patient_id": 3,
  "measurement_type": "ecg"
}
{
  "id": 3,
  "measurement": 30.5,
  "sequence": 3,
  "time_stamp": "2016-05-25T04:53:38.000Z",
  "device_id": 2,
  "patient_id": 3,
  "measurement_type": "ecg"
}

# need to return this structure via GET
{
  "max_timestamp": "2020-05-25T04:53:38.000Z",
  "measurement_type": "ecg",
  "measurements": [
    { measurement: 10.5, sequence: 1, time_stamp: "2020-05-25T04:53:38.000Z" },
    { measurement: 20.5, sequence: 2, time_stamp: "2016-05-25T04:53:38.000Z" },
    { measurement: 30.5, sequence: 3, time_stamp: "2012-05-25T04:53:38.000Z" }
  ]
}

目前我有這個：

class PatchDataSerializer < ActiveModel::Serializer
  attributes :max_timestamp, :measurement_type, :measurements

  def measurements
    [{ :measurement => object.measurement, :sequence => object.sequence, :time_stamp => object.time_stamp.to_i }]
  end

  def max_timestamp
  end

end

正在返回：

[
  {
    "max_timestamp": null,
    "measurement_type": "ecg",
    "measurements": [
      {
        "measurement": 20.5,
        "sequence": 5,
        "time_stamp": 1464152018
      }
    ]
  },
  {
    "max_timestamp": null,
    "measurement_type": "ecg",
    "measurements": [
      {
        "measurement": 20.5,
        "sequence": 5,
        "time_stamp": 1464152018
      }
    ]
  }
]

如您所見，這不起作用。 我最大的問題是如何將每一行的measurements推入一個陣列中？ 我還需要為整個請求而不是每一行返回一次max_timestamp 。

任何幫助是極大的贊賞。

Answer 1

您可以為要序列化的類創建一個自定義類方法，如下所示（我假設您要按類型進行過濾？）

def self.measurements_of_type(type)
  {
    max_timestamp: Class.maximum(:time_stamp),
    measurement_type: type
    measurements: Class.where(type: type).select(:measurement, :sequence, :time_stamp)
  }
end

Answer 2

在我看來，您可以創建一個新類來處理來自測量的數據聚合，然后為該類創建一個序列化器。

取決於您所使用的AMS版本，可以采用不同的方式進行操作，但要點很明顯

class MeasurementsAggregation
  attr_reader :measurements, :type, :max_timestamp

  def initialize(type, measurements)
    @measurements = measurements
    @max_timestamp = measurements.max_by(&:updated_at).updated_at
    @type = type
  end
end

那么您的序列化器將是

class MeasurementsAggregationSerializer < ActiveModel::Serializer
  attributes :max_timestamp, :type

  has_many :measurements, serializer: MeasurementSerializer
end

您的測量序列化器將是

class MeasurementSerializer < ActiveModel::Serializer
  attributes :measurement, :sequence, :time_stamp
end

您可能需要做一些調整才能使PORO與AMS一起工作，但這應該是它的要旨。