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Some Rails Validations

• Here are some examples of Rails validations:
  

  # Insure that field is nonempty.
  validates :name, presence: true
  
  # Insure that field is unique (not equal to 
  # an existing value) in the table.
  validates :ssn, uniqueness: true
  
  # Insure that field value is not in a given set:
  validates :credit_card, exclusion: { in: %w( DinersClub
    Discover MasterCard), message: "${value} not accepted." }
  
  # Insure output is accepted by a regular expression.
  validates :phone, format: { with: /\A\d{3}\/\d{3}-\d{4}\Z/, 
    message: " number not legal." }
    
  # Insure that field value is in a given set:
  validates :size, inclusion: { in: %w( small medium large ), 
    message: "#{value} should be small, medium, or large." }
  
  # Control the size in characters of string input:
  validates :bio, length: { maximum: 500 }
  validates :passwd, length: { minimum: 8 }
  validates :id_num, length: { in 6:12 }
  validates :id_num, length: { is: 10 }
  
  # Insures that the input is a number:
  validates :gpa, numericality: true
  validates :gpa, numericality: { 
     greater_than_or_equal_to: 0.0,
     less_than_or_equal_to: 4.0 }
  validates :age, numericality: { 
     integer_only: true }
  # greater_than, less_than, equal_to, 
  # odd, or even are also options.
  

• Reference: guides.rubyonrails.org/active_record_validations.html