Mongoid puts float values on fields when string is given

Question

I am using Ruby 1.9.3-p448 and Rails 3.2.13. I have this simple model with a float format validation:

class User
  include Mongoid::Document
  include Mongoid::Timestamps

  field :height, type: Float
  field :weight, type: Float

  validates :height, presence: true, format: { with: /[-+]?[0-9]*\.?[0-9]+/ }
  validates :weight, presence: true, format: { with: /[-+]?[0-9]*\.?[0-9]+/ }

end

If i run this code:

test = User.new(height:"hi", weight:"try")

It gives me the following result:

#<User _id: 51f67b49781018056b000008, created_at: nil, updated_at: nil, height: 0.0,width: 0.0>

Why does mongoid put a 0.0 value if I put a string? I was expecting a validation error.

also when i run User.validators on console it prints [#<Mongoid::Validations::PresenceValidator:0xa7e51d0 @attributes=[:height], @options={}>, # <Mongoid::Validations::PresenceValidator:0xa7e38d0 @attributes=[:weight], @options={}>, #<Mongoid::Validations::PresenceValidator:0xa907824 @attributes=[:chest], @options={}>] — Alberto Pellizzon
– Alberto Pellizzon, Commented Jul 29, 2013 at 15:17

toro2k · Accepted Answer · 2013-07-29 15:53:13Z

3

You get no validation error because the method new doesn't trigger the validation, to see it you should execute:

User.create!(height:"hi", weight:"try")
# .../mongoid-3.1.0/lib/mongoid/persistence.rb:335:in `fail_validate!': (Mongoid::Errors::Validations)
# Problem:
#   Validation of User failed.
# Summary:
#   The following errors were found: Height is invalid, Weight is invalid
# ...

Given that, the fields height and weight are filled with 0.0 because the Strings are converted to Float using the to_f method, that behaves like this:

'foo'.to_f
# => 0.0

Moreover, it is useless to validate a floating point field using a regular expression because the conversion to Float is performed before the validation, so the validation always fails because of the behaviour of =~:

1.2 =~ /any_regexp/
# => nil

Update To validates that, given as string, the field is a valid number you can use the numericality option:

class User
  # ...
  validates :height, presence: true, numericality: true
  # ...
end

User.create!(height: '0.0')
# => #<User ... >

User.create!(height: 'foo')
# Problem:
#  Validation of User failed.
# ...

edited Jul 29, 2013 at 15:53

answered Jul 29, 2013 at 15:20

toro2k

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1 Comment

Alberto Pellizzon Over a year ago

Thats exactly my problem thank you! So i must check the format in client side or cani do it in server side by another way?

Community · Accepted Answer · 2017-05-23 10:25:16Z

-1

MongoDB stores data in a binary format called BSON which supports these numeric data types:

int32 - 4 bytes (32-bit signed integer)
int64 - 8 bytes (64-bit signed integer)
double - 8 bytes (64-bit IEEE 754 floating point)

There's no exact value fixed-point equivalent to mySQL's decimal type in MongoDB, but you can store 64-bit floating point numbers in Mongo as a double.

It's worth mentioning that the MongoDB shell - being a JavaScript shell - doesn't recognise the distinction between integer and floating-point values, it treats all numbers the same because JavaScript represents all numbers as 64-bit floating point, regardless of their underlying BSON type.

Most MongoDB language drivers, however, make the distinction between integer and floating point types.

From -> Does MongoDB support floating point types?

edited May 23, 2017 at 10:25

CommunityBot

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answered Jul 29, 2013 at 14:41

Mini John

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2 Comments

Alberto Pellizzon Over a year ago

i am using mongoid and i cant specity Double as data type i have only Flaot two.mongoid.org/docs/documents/fields.html

Jon Cairns Over a year ago

Downvoted, because it's an exact copy of this answer. If the answer should have been the same then just link to the other question.

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