a rails model used to create all "validates_numericality_of" validations based on the schema. The code sux a bit, and have a lot of smells, but is working by now...

runner.rb

class TheModel

  def name
    @model_name
  end

  def initialize(line)
    @model_name = extract_name(line).to_s.singularize
  end

  def add(line)
    if has_integer? line
      (@integers ||= []) << extract_name(line)
    elsif has_decimal? line
      (@decimals ||= []) << extract_decimal(line)
    end
  end

  def to_s(abc = nil)
    puts %(#{@model_name}
            .... @integers = #{@integers.inspect}
            .... @decimals = #{@decimals.inspect})
  end

  def integer_validation
    "validates_numericality_of #{@integers.to_s[1..-2]}, :allow_nil => true" if has_integers?
  end

  def decimal_validation
    "validates_numericality_of #{@decimals.collect{|i| i[:column]}.to_s[1..-2]}, :allow_nil => true, :less_than => 100000000" if has_decimals?
    # if @decimals
    #   # @inverted = @decimals.invert
    #   # @inverted.

    # end
  end

  def has_anything?
    has_integers? or has_decimals?
  end

  def self.is_table(line)
    line =~ /create_table/
  end

  def self.is_allowed(line, to_skip)
    to_skip.none?{|w| /#{w}/ =~ line}
  end

  def remove(property)
    @decimals.delete(property) if @decimals
    @integers.delete(property) if @integers
  end

private

  def has_integers?
    @integers and [email protected]?
  end

  def has_decimals?
    @decimals and [email protected]?
  end

  def has_integer?(line)
    line =~ /\.integer/
  end

  def has_decimal?(line)
    line =~ /\.decimal/
  end

  def extract_name(line)
    line.gsub( /"(.*)"/ ).first.gsub(/"/, "").to_sym
  end

  def extract_decimal(line)
    {:column => extract_name(line),
    :options => eval("{#{line.gsub( /:.*$/ ).first}}")}
  end

end

class Runner

  def self.run
    schema_path = "db/schema.rb"
    models_folder_path = "app/models"
    to_skip = %w(session)

    f = File.open(schema_path)
    while (l = f.gets)
      #change me :/
      if TheModel.is_table(l) and TheModel.is_allowed(l, to_skip)
        @last_model = TheModel.new(l)
        (@models ||= []) << @last_model
      end
      @last_model.add(l) if @last_model
    end

    @models.each do |m|
      
      m.name.camelize.constantize.validators.each do |validator|
        if validator.is_a? ActiveModel::Validations::NumericalityValidator
          validator.attributes.each do |validator_attribute|
            m.remove(validator_attribute)
          end
        end
      end

      @models.delete(m) unless m.has_anything?
    end

    @models.each do |m|
      File.open("#{models_folder_path}/#{m.name}.rb", 'r+') do |f|   
        out = ""
        f.each_with_index do |line, index|
          if index == 2
            out << "  #{m.integer_validation}\n" if m.integer_validation
            out << "  #{m.decimal_validation}\n" if m.decimal_validation
          end
          out << line
        end
        f.pos = 0                     
        f.print out
        f.truncate(f.pos)             
      end
    end

  end

end