How to filter by foreign id and local attribute via belongs_to? - ruby

Question

The following models are linked via belongs_to:
require 'mongoid'
class Sensor
include Mongoid::Document
field :sensor_id, type: String
validates_uniqueness_of :sensor_id
end
...
require 'mongoid'
require_relative 'sensor.rb'
class SensorData
include Mongoid::Document
belongs_to :sensor
field :date, type: Date
field :ozonMax1h, type: Float
field :ozonMax8hMittel, type: Float
index({ date: 1, sensor_id: 1 }, { unique: true })
end
Here is a Sinatra app which provides a few API paths based on these models:
require 'sinatra'
require 'csv'
require_relative './models/sensor.rb'
require_relative './models/sensor_data.rb'
configure do
Mongoid.load!('./mongoid.yml')
end
def prepare_for_export(sensor_data)
converted_data = sensor_data.asc(:date).map do |e|
{
sensor_id: e.sensor.nil? ? :null : e.sensor.sensor_id,
date: e.date,
ozonMax1h: e.ozonMax1h,
ozonMax8hMittel: e.ozonMax8hMittel
}
end
converted_data
end
def convert_to_json(sensor_data)
prepare_for_export(sensor_data).to_json
end
def convert_to_csv(sensor_data)
data = prepare_for_export sensor_data
csv_string = CSV.generate do |csv|
csv << data.first.keys
data.each do |hash|
csv << hash.values
end
end
csv_string
end
def get_recent
max_date = SensorData.max(:date)
SensorData.where(date: max_date)
end
def get_for_year(year)
SensorData.where(:date.gte => Date.new(year, 1, 1)).where(:date.lte => Date.new(year, 12, 31))
end
def get_for_sensor(sensor)
foo = SensorData.where(sensor_id: sensor)
puts "hallo"
return foo
end
get '/api/v1/stations' do
content_type :json
Sensor.all.map { |e| {sensor_id: e.sensor_id} }.to_json
end
get '/api/v1/sensordata/:year' do
content_type :json
convert_to_json get_for_year(params[:year].to_i)
end
get '/api/v1/sensordata/:year/csv' do
convert_to_csv get_for_year(params[:year].to_i)
end
get '/api/v1/recent' do
content_type :json
convert_to_json get_recent
end
I would like to output the SensorData for a particular sensor such as here:
/api/v1/stations/:sensor_id/sensordata/:year/csv

Answer 1

I am not sure what you are trying to do or even if you are still looking for an answer but here it goes. Something seems wrong with the models in the example you have here. Sounds like part of what you are doing would work if Sensor knows about sensor_data. So might need to add this to Sensor class:
has_many :sensor_data
Though the singular of data is datum. The class would be expected to be SensorDatum. If you can't change it, you need to tell Mongoid the class_name to expect in the has_many is actuall SensorData.
You CAN specify foreign_key in Mongoid with belongs_to.
You CANNOT filter with the belongs_to like you can with ActiveRecord, but you can use scopes outside of the belongs_to to get the same effect. Exampe:
belongs_to :sensor
scope :for_year, -> (year) { where(:date.gte => Date.new(2015,1,1)).where(:date.lte => Date.new(2015, 12, 31))}
or
belongs_to :sensor
def self.for_year year
where(:date.gte => Date.new(year,1,1)).where(:date.lte => Date.new(year, 12, 31))
end
So your query would become something like this:
sensor = Sensor.find_by(sensor_id: params[:sensor_id])
sensor.sensor_data.for_year(2015)