Question

How to extract and save array from string parameter? I’m trying convert string beafore_create but this doesn’t work. When I comment before_create :waypoints Mongoid throw error:

Parameters: {
    "utf8"=>"✓", 
     "authenticity_token"=>"nehoT1fnza/ZW4XB4v27uZsfFjjOu/ucIhzMmMKgWPo=", 
     "trip"=>{
         "title"=>"test", 
         "description"=>"test", 
         "waypoints"=>"[[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]]"
     }
}

Completed 500 Internal Server Error in 1ms

Mongoid::Errors::InvalidType (Field was defined as a(n) Array, but received a String with the value "[[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]]".):

EDIT Thanks for help, now it work but I don’t know whether following approach is good. I remove before_create and change parameter name from waypoints to waypoints_s and def waypoints to def waypoints_s:

#Parameters:
#"waypoints"=>"[[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]]"
"waypoints_s"=>"[[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]]"

class Trip
  include Mongoid::Document
  field :title, :type => String
  field :description, :type => String
  field :waypoints, :type => Array

  #before_create :waypoints

  #def waypoints=(arg)
  def waypoints_s=(arg)
    if (arg.is_a? Array)
      #@waypoints = arg
      self.waypoints = arg
    elsif (arg.is_a? String) 
      #@waypoints = arg.split(',')
      self.waypoints = JSON.parse(arg)
    else 
      return false 
    end 
  end
end

class TripsController < ApplicationController
  def create
    @trip = Trip.create(params[:trip])
    @trip.save
  end
end

Answer 1

Parse the string as a JSON object:

require 'json'

waypoints = "[[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]]"
JSON.parse(waypoints)

=> [[52.40637, 16.92517], [52.40601, 16.925040000000003], [52.405750000000005, 16.92493], [52.40514, 16.92463], [52.404320000000006, 16.924200000000003]]