Question

I have the following rails model:

class Product < ActiveRecord::Base
end

class CreateProducts < ActiveRecord::Migration
  def self.up
    create_table :products do |t|
      t.decimal :price

      t.timestamps
    end
  end

  def self.down
    drop_table :products
  end
end

But when I do the following in the rails console:

ruby-1.9.2-p180 :001 > product = Product.new
 => #<Product id: nil, price: nil, created_at: nil, updated_at: nil> 
ruby-1.9.2-p180 :002 > product.price = 'a'
 => "a" 
ruby-1.9.2-p180 :003 > product.save
 => true 
ruby-1.9.2-p180 :004 > p product
#<Product id: 2, price: #<BigDecimal:39959f0,'0.0',9(9)>, created_at: "2011-05-18 02:48:10", updated_at: "2011-05-18 02:48:10">
 => #<Product id: 2, price: #<BigDecimal:3994ca8,'0.0',9(9)>, created_at: "2011-05-18 02:48:10", updated_at: "2011-05-18 02:48:10"> 

As you can see, I wrote ‘a’ and it saved 0.0 in the database. Why is that? This is particularly annoying because it bypasses my validations e.g.:

class Product < ActiveRecord::Base
  validates :price, :format => /\d\.\d/
end

Answer 1

anything that is invalid gets cast to 0.0 if you call to_f on it

"a".to_f #=> 0.0

you would need to check it with validations in the model

validates_numericality_of :price # at least in rails 2 i think

i dont know what validating by format does, so i cant help you there, but try to validate that it is a number, RegExs are only checked against strings, so if the database is a number field it might be messing up

:format is for stuff like email addresses, logins, names, etc to check for illegeal characters and such