Field with possible different types mongoid

Question

In my model I have

field :is_open, type: Time, default: nil

However previously in this same model, I stored this type as a boolean. I now want to change it to type Time. For new items in my database this works fine, however for old records where it's still stored as a boolean, when I try to access this attribute

modelInstance.is_open

I get the following error:

#<NoMethodError: undefined method `getlocal' for true:TrueClass>

Instead of changing all the booleans in my mongo database to Time objects, is there a way/hook I can do on mongo so that when this attribute is pulled from the document, I can check if it's a boolean and replace it with a timestamp?

Eventually I will write a migration script, but for now I cannot change the format of my database. — user2333700, Sep 19 '14 at 04:15
http://stackoverflow.com/questions/9389548/change-type-of-field-in-mongoid-without-losing-data — Igor Guzak, Sep 19 '14 at 05:36
@IS04 Yeah but that sort of violates the "cannot change the format of my database" restriction, no? — mu is too short, Sep 19 '14 at 05:37

mu is too short · Accepted Answer · 2014-09-19T21:57:23.500

You don't have to specify the field type with Mongoid. That means that you can do things like this:

class Model
  include Mongoid::Document
  field :f
end

with data like this:

> db.models.find()
{ "_id" : ObjectId(...), "f" : true }
{ "_id" : ObjectId(...), "f" : 6 }
{ "_id" : ObjectId(...), "f" : "pancakes" }

And everything will work out just fine:

rails > Model.all.map { |m| puts "#{m.f.class} - #{m.f.inspect}" }
TrueClass - true
Float - 6.0
String - "pancakes"

So you can drop the :type from your field and everything should work okay. Of course, you might want to provide your own def is_open and def is_open= methods if you need to do some sort of manual type conversion or checking while you're waiting to fix up your MongoDB data.

Field with possible different types mongoid

1 Answers1