How to save received string parameters in array field?

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

vise · Accepted Answer · 2011-11-13 13:17:49Z

2

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]]

answered Nov 13, 2011 at 13:17

vise

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1 Comment

leon Over a year ago

It works well in console but in befor_create method rails ignore it and save all data without waypoints.

megas · Accepted Answer · 2011-11-13 13:14:28Z

1

You need to use serialize http://api.rubyonrails.org/classes/ActiveRecord/Base.html#method-c-serialize

This method serialize your object to database by YAML format (let's say just text with some format).

class Trip < ActiveRecord::Base

  serialize :waypoints

end

trip = Trip.create( :waypoints => [[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]])

Trip.find(trip.id).waypoints # => [[52.40637,16.92517],[52.40601,16.925040000000003],[52.405750000000005,16.92493],[52.40514,16.92463],[52.404320000000006,16.924200000000003]]

edited Nov 13, 2011 at 13:14

answered Nov 13, 2011 at 12:22

megas

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2 Comments

leon Over a year ago

I found that in Mongoid I can store array fields without serialization. My problem still exist i think that some way convert waypoints parameter from string to array or remove quotes?

megas Over a year ago

The serialize method is making converting for you, you're just using waypoints like it's usual array. For me using serialization is more neat way then using for example json, because you don't need to parse, to convert something.

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