Question

I have decimal field in my DB. Users can input values in two formats: with comma or point (11,11 or 11.11).

But MySQL allows to save data only in ‘point’ format, so i want to process data before saving with regex like this:

sub(/,/,".")

How can i do it in Rails3?

Answer 1

If I understand you correctly, this could be done in the controller or the model. I might use the before_save callback in the model to achieve this in the following way:

class Item < ActiveRecord::Base
  before_save :standardise_numbers
  ...

  protected
  
  # Called before this object is saved to the DB
  def standardise_numbers
    self.number.sub!(",", ".")
  end
end

Where number is the attribute you’re wanting to convert.

I assume you don’t need to convert it back to comma representation to display to the user? If you do, you may want to look into the internationalisation API for Rails, Il8n. It handles this kind of stuff and more, so definitely worth looking into.

Alternative Solution (edit)

Based on your feedback, my above solution doesn’t work since the number is already converted and the decimal part lost when it is passed into the model. A similar piece of code could be used in the controller to intercept and convert the number in the params hash itself:

class PostController < ActionController
  before_filter :standardise_numbers, :only => [ :create, :update ]
  
  def create
    @post = Post.create(params[:post])
  end

  protected
  
  # Intercepts the params hash
  def standardise_numbers
    params[:post][:number].sub!(",", ".")
  end
end

This simplifies the create and update methods, allowing you to deal with the hash in the same way you normally would.