Validation in Rails 3

• :presence => true
• :uniqueness => true
• :numericality => true
• :length => { :minimum => 0, maximum => 2000 }
• :format => { :with => /.*/ }
• :inclusion => { :in => [1,2,3] }
• :exclusion => { :in => [1,2,3] }
• :acceptance => true
• :confirmation => true

Example

validates :login, :presence => true, :length => {:minimum => 4},
          :uniqueness => true, :format => { :with => /[A-Za-z0-9]+/ }