Why do I need to put my code in a PRE tag? Surely the comment editor knows I’m going to be typing in code!

Sorry, couldn’t resist

Assuming vehicle is an instance of Vehicle and there’s an appropriate error checking before hand, then the only important line of code is this:

vehicle.miles = param[:vehicle][:miles].gsub(/,/, '').to_i

But, this is pretty lame for a challenge.

Change #1 to be, “the most elegant solution to parse HUMAN numbers” and it’ll be a little better.

Human numbers being the stuff people normally enter, like “15,000” or “15,000KM” or “15,000 miles”

class Vehicle < ActiveRecord::Base before_save :normalize_miles end

def normalize_miles
  self.miles.gsub!(',','')
end

In the Vehicle model:

def miles=(inputted_miles)
    write_attribute(:miles, String(inputted_miles).delete("^0-9"))
 end

This takes the user-given value and strips all non-digits (commas and units) from it. Another method could be used to format the value when retrieved (def miles … end)

self.miles = miles.gsub(/[^0-9]/, "") 

String.gsub is great but String.delete is also helpful here, and perhaps more readable.

For any of the gsub examples above, you could use delete instead, like this:

miles = miles.delete(',')

will work.

Chris Lloyd is closest to my preferred solution, but I normalize prior to the validation, rather than the save.

class Vehicle < ActiveRecord::Base
  before_validation :normalize_miles

  validates_format_of :miles, :with => /\d*/

private

  def normalize_miles
    self.miles = miles.delete("^0-9")
  end

end

I’m too tired to type actual code, but i would check if the data is ONLY numbers and commas. If so, I would strip the commas out, make an int, and be happy. If not, i would alert the user that he entered something wrong.

If you strip out decimals, then 1005.5 becomes 10055. Arron had it right by stripping out the comma but then doing to_i to get rid of the decimal. However, the code should probably go in the model instead of the controller.

if you’re in JRuby, NumberFormat offers a nice locale sensitive solutions (where commas and dots have the appropriate meaning in places where the comma is the decimal point equivalent).

Of course, it’s far from elegant!!!

try {
  NumberFormat  nf = NumberFormat.getNumberInstance();
  Number n = nf.parse(miles); 
  //note that getting that miles string isn't as easy as it looks
}
catch (ParseException p) {
  //this bit might get tricky
}

I think, the very first thing should be to give a kick within the client side UI itself, why to put the “MUST” extra work on the server. More or less whatever mentioned above is a tweak or FIX we are doing for the value that user has entered without letting the user know that there might be some tweaking going to happen with the data he entered. Of course there should be such a code in the model but things should also be handled within the browser using JS.

In my rails applications I always handle such things with a simple function by capturing the onKeyUp event on the text field. And the functionality should also work on everything apart from 0-9 if we are considering the integer, not only the commas but any other character but numeral.

So, the best here, and what I do is two things…

Client Side JS code

specifying in the text_field or text_field_tag options as

 :onkeyup => "check_integer(this)" 

adding the JS function

 function check_integer(el)
 {
  if(String(parseInt(el.value))=="NaN")
    el.value = '';
  else
    el.value = parseInt(el.value);
 }

This JS function will automatically remove any character other than 0-9 and will left a valid numeric value in the text field while the user is typing in the box.

Server side Ruby code

definitely I will go with the more generic “gsub” to swipe out anything other than 0-9

 def normalize_miles
   self.miles.gsub!(/[^0-9]/, '')
 end

Stupidity is the property a person, action or belief instantiates by virtue of having or being indicative of low intelligence or poor learning abilities.

I came into a problem like this in a recent project. There was a model called Sale which had a price, represented by a number without decimals and using dots instead of commans for hundred separation (used in Spain). The model looked like this:

class Sale < ActiveRecord::Base
  before_validation :remove_price_dots

  validates_presence_of :price
  validates_numericality_of :price

  def remove_price_dots
    self.price = price.delete(".")
    # I don't want to stripe out all non-number characters with grep(/[^\d]/, '') because
    # the user might be typing 'I walked 5 miles from home' and it would be valid
  end

  def price
    price.to_i.to_s.reverse.split('').in_groups_of(3,false).collect{|g| g.to_s}.join('.').reverse
    # for an amount of 50000 it will show 50.000, this will be used in update forms as well
    # It might exists another simpler solution for this
  end
end

I wrote a plugin to accomplish this same task for currency fields, where an amount needs to be entered in dollars. Users will often use a ’$’ to enter the number. The code can be found here:

http://github.com/faithfulgeek/acts_as_currency/tree

Just a complement on this post Jeff…I get so disappointed when I run into user interfaces like the horrid one you showed us.

As is shown in the writings of Galileo, our ideas stand in need to general logic.