Rails 5.0 nested Reform

Question

I have 2 model with the following details:

# Device model
module Rubywebit::Devices
  class SensorValue < ApplicationRecord
    belongs_to :device, class_name: Rubywebit::Devices::Device
  end
end

# SensorValue model
module Rubywebit::Devices
  class Device < ApplicationRecord
    has_many :sensor_values, class_name: Rubywebit::Devices::SensorValue
  end
end

I am using Reform gem (https://github.com/apotonick/reform) to create form objects. My form classes for 2 model is the following code:

# Device form
class DeviceForm < Reform::Form
  property :name
  property :imei
  collection :sensor_values, form: SensorValueForm
end

# SensorValue form
class SensorValueForm < Reform::Form
  property :index
  property :value
  property :date_time
end

As you see I have 2 nested form for 2 model. In step 1 one record insert in to table with references:

df=DeviceForm.new(Rubywebit::Devices::Device.new, sensor_values: [Rubywebit::Devices::SensorValue.new]) 
df.validate(name: 'A',imei:'B',sensor_values: [index: 1, value: 2])
df.save

output is:

(0.6ms)  BEGIN
  SQL (0.5ms)  INSERT INTO "rubywebit_devices_devices" ("name", "imei", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETUR
NING "id"  [["name", "A"], ["imei", "B"], ["created_at", 2016-06-14 05:04:58 UTC], ["updated_at", 2016-06-14 05:04:58 UTC]]
  SQL (0.5ms)  INSERT INTO "rubywebit_devices_sensor_values" ("index", "value", "device_id", "created_at", "updated_at") VALUES (
$1, $2, $3, $4, $5) RETURNING "id"  [["index", 1], ["value", 2.0], ["device_id", 2], ["created_at", 2016-06-14 05:04:58 UTC], ["u
pdated_at", 2016-06-14 05:04:58 UTC]]
   (0.8ms)  COMMIT
   (0.1ms)  BEGIN
   (0.1ms)  COMMIT

and this is OK.

And in step 2 we have a record for device and I want to insert a record to sensor_values table with the device_id that we have:

df=DeviceForm.new(Rubywebit::Devices::Device.find(1), sensor_values: [Rubywebit::Devices::SensorValue.new])
df.validate(sensor_values: [index: 2, value: 3])
df.save

output:

Rubywebit::Devices::SensorValue Load (0.4ms)  SELECT "rubywebit_devices_sensor_values".* FROM "rubywebit_devices_sensor_values"
 WHERE "rubywebit_devices_sensor_values"."device_id" = $1  [["device_id", 1]]
   (0.2ms)  BEGIN
  SQL (13.1ms)  UPDATE "rubywebit_devices_sensor_values" SET "device_id" = NULL WHERE "rubywebit_devices_sensor_values"."device_i
d" = $1 AND "rubywebit_devices_sensor_values"."id" = 17  [["device_id", 1]]
  SQL (0.5ms)  INSERT INTO "rubywebit_devices_sensor_values" ("index", "value", "device_id", "created_at", "updated_at") VALUES (
$1, $2, $3, $4, $5) RETURNING "id"  [["index", 1], ["value", 2.0], ["device_id", 1], ["created_at", 2016-06-14 05:19:51 UTC], ["u
pdated_at", 2016-06-14 05:19:51 UTC]]
   (0.6ms)  COMMIT
   (0.1ms)  BEGIN
   (0.1ms)  COMMIT
   (0.1ms)  BEGIN
   (0.1ms)  COMMIT

As you see, Reform does an additional transaction (UPDATE "rubywebit_devices_sensor_values" ...) why?

Answer 1

I solved this problem by Populate_if_empty feature.

https://github.com/trailblazer/reform/issues/370