Data transformation after successful validation

Question

I'm having a bit of a problem normalizing a UPC string code so that I can store it in the same format in the database.

I'm using the ean gem to check if the string is good (which is working fine), but if I throw some assignment code after it validates such as:

validate :upc_check

def upc_check
    if !upc.nil?
        if !upc.ean?
            errors.add(:upc, 'is not a valid UPC.')
        else
            upc = upc.strip
        end 
    end 
end 

The strip call is just an example as it's a string. I'll actually be removing the dashes in the upc.

The above code doesn't work so well as it doesn't actually save it. I had a look at triggering a method like

after_validation :normalize_upc

def normalize_upc
    upc = upc.strip
end

..but the above doesn't work either.

What do you guys do to validate and transform data after validation?

Answer 1

I would make my validator strict, and then use a before_validation filter to do any necessary transformations.

Answer 2

I would recommend overriding the setter method in your model for upc and not having a separate method for normalizing it. This would be accomplished with something like:

def upc=(value)
  self.upc = value.strip
end

Edit:

I would also clean up your validation method to remove this functionality like so:

validate :upc_check, :unless => lambda {|m| m.upc.nil?}

def upc_check
  errors.add(:upc, 'is not valid') unless upc.ean?
end