Ruby on Rails URL, Email, and IP Validation
Validating an Email Address
validates_format_of(:email, :with => /^([^@s]+)@((?:[-a-z0-9]+.)+[a-z]{2,})$/i, :on => :create, :message=>"has an invalid format")
Validating URLs
validates_format_of :url, :with => /^(https?://)?([^/]+)(/.+)?$/i # OR validates_format_of :url, :with => /^(ftp|https?)://((?:[-a-z0-9]+.)+[a-z]{2,})/
Validating IP addresses
validates_format_of :ip, :with => /^(d{1,3}.d{1,3}.d{1,3}.d{1,3})?$/