RoR Validations

gistfile1.rb

# Validate the length of the string

validates_length_of :username, :minimum => 5, :maximum => 255, :allow_blank => false

# or
validates :password, :length => { :minimum => 6 }, allow_blank: true

# Validate paperclip attachment

validates_attachment :profile_image,
                    :content_type => { :content_type => ["image/jpg", "image/jpeg", "image/png", "image/bmp", "image/gif"] },
                    :size => { :in => 0..10.megabytes }
                    
# Custom Validation

validate :cities_validation
def cities_validation
  if default_city_id.present? && (!City.pluck(:id).include? default_city_id)
    errors.add(:default_city_id, "default_city_id is not valid.")
  end
end

# uniqueness validation on one attr
validate :facebook_id, :uniqueness => true

# Before Validation Callback
before_validation(:on => :create)  { |user| user.email = email.downcase rescue nil }