Validation

_form.html.erb

<%= semantic_form_for([@customer, @phone]) do |f| %>
  <%= f.semantic_errors :state %>

  <%= f.inputs do %>
    <%= f.input :number, as: :string, input_html: { maxlength: 18 }%><br />
    <%= f.input :extension, as: :number %><br />
    <%= f.input :number_type, as: :select, collection: Phone.number_type_name_options %>
  <% end -%>
  <%= f.actions %>
<% end %>

phone.rb

class Phone < ActiveRecord::Base
  belongs_to :customer
  attr_accessible :number, :number_type, :extension

  NUMBER_TYPE_NAMES = {1 => 'Home', 2 => 'Work', 3=> 'Cell'}

  def number_type_name
    NUMBER_TYPE_NAMES[self.number_type]
  end

  def self.number_type_name_options
    options = {}
    NUMBER_TYPE_NAMES.sort.each {|i, v| options[v] = i }
    return options
  end

  before_validation :strip_non_numeric
  validates :number, 
    presence: true, 
    length: { minimum: 7, maximum: 11 },
    numericality: { only_integer: true }
  validates :extension, 
    allow_blank: true, 
    numericality: { only_integer: true }
  validates :number_type,
    allow_blank: false,
    numericality: { only_integer: true }

  protected
  def strip_non_numeric
    number.to_s.gsub! /\D/, ''
    number = number.to_i
  end
end

validation error

New phone
 
Number* [(123) 457 - 7890]
is too short (minimum is 7 characters) and is not a number

Extension [123]

Number type [Work |v]

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