class User < ActiveRecord::Base 
  # Max & min lengths for all fields 
  SCREEN_NAME_MIN_LENGTH = 4 
  SCREEN_NAME_MAX_LENGTH = 20 
  PASSWORD_MIN_LENGTH = 4 
  PASSWORD_MAX_LENGTH = 40 
  EMAIL_MAX_LENGTH = 50 
  SCREEN_NAME_RANGE = SCREEN_NAME_MIN_LENGTH..SCREEN_NAME_MAX_LENGTH 
  PASSWORD_RANGE = PASSWORD_MIN_LENGTH..PASSWORD_MAX_LENGTH 
  
  validates_uniqueness_of :screen_name, :email 
  validates_length_of :screen_name, :within => SCREEN_NAME_RANGE
  validates_length_of :password, :within => PASSWORD_RANGE 
  validates_length_of :email, :maximum => EMAIL_MAX_LENGTH 
  validates_presence_of :email 
end