method

validates_length_of

v2.3.8 - Show latest stable - Class: ActiveRecord::Validations::ClassMethods

validates_length_of(*attrs)

public

Validates that the specified attribute matches the length restrictions supplied. Only one option can be used at a time:

  class Person < ActiveRecord::Base
    validates_length_of :first_name, :maximum=>30
    validates_length_of :last_name, :maximum=>30, :message=>"less than {{count}} if you don't mind"
    validates_length_of :fax, :in => 7..32, :allow_nil => true
    validates_length_of :phone, :in => 7..32, :allow_blank => true
    validates_length_of :user_name, :within => 6..20, :too_long => "pick a shorter name", :too_short => "pick a longer name"
    validates_length_of :fav_bra_size, :minimum => 1, :too_short => "please enter at least {{count}} character"
    validates_length_of :smurf_leader, :is => 4, :message => "papa is spelled with {{count}} characters... don't play me."
    validates_length_of :essay, :minimum => 100, :too_short => "Your essay must be at least {{count}} words."), :tokenizer => lambda {|str| str.scan(/\w+/) }
  end

Configuration options:

:minimum - The minimum size of the attribute.
:maximum - The maximum size of the attribute.
:is - The exact size of the attribute.
:within - A range specifying the minimum and maximum size of the attribute.
:in - A synonym(or alias) for :within.
:allow_nil - Attribute may be nil; skip validation.
:allow_blank - Attribute may be blank; skip validation.
:too_long - The error message if the attribute goes over the maximum (default is: "is too long (maximum is {{count}} characters)").
:too_short - The error message if the attribute goes under the minimum (default is: "is too short (min is {{count}} characters)").
:wrong_length - The error message if using the :is method and the attribute is the wrong size (default is: "is the wrong length (should be {{count}} characters)").
:message - The error message to use for a :minimum, :maximum, or :is violation. An alias of the appropriate too_long/too_short/wrong_length message.
:on - Specifies when this validation is active (default is :save, other options :create, :update).
:if - Specifies a method, proc or string to call to determine if the validation should occur (e.g. :if => :allow_validation, or :if => Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.
:unless - Specifies a method, proc or string to call to determine if the validation should not occur (e.g. :unless => :skip_validation, or :unless => Proc.new { |user| user.signup_step <= 2 }). The method, proc or string should return or evaluate to a true or false value.
:tokenizer - Specifies how to split up the attribute string. (e.g. :tokenizer => lambda {|str| str.scan(/\w+/)} to count words as in above example.) Defaults to lambda{ |value| value.split(//) } which counts individual characters.

# File activerecord/lib/active_record/validations.rb, line 638
      def validates_length_of(*attrs)
        # Merge given options with defaults.
        options = {
          :tokenizer => lambda {|value| value.split(//)}
        }.merge(DEFAULT_VALIDATION_OPTIONS)
        options.update(attrs.extract_options!.symbolize_keys)

        # Ensure that one and only one range option is specified.
        range_options = ALL_RANGE_OPTIONS & options.keys
        case range_options.size
          when 0
            raise ArgumentError, 'Range unspecified.  Specify the :within, :maximum, :minimum, or :is option.'
          when 1
            # Valid number of options; do nothing.
          else
            raise ArgumentError, 'Too many range options specified.  Choose only one.'
        end

        # Get range option and value.
        option = range_options.first
        option_value = options[range_options.first]
        key = {:is => :wrong_length, :minimum => :too_short, :maximum => :too_long}[option]
        custom_message = options[:message] || options[key]

        case option
          when :within, :in
            raise ArgumentError, ":#{option} must be a Range" unless option_value.is_a?(Range)

            validates_each(attrs, options) do |record, attr, value|
              value = options[:tokenizer].call(value) if value.kind_of?(String)
              if value.nil? or value.size < option_value.begin
                record.errors.add(attr, :too_short, :default => custom_message || options[:too_short], :count => option_value.begin)
              elsif value.size > option_value.end
                record.errors.add(attr, :too_long, :default => custom_message || options[:too_long], :count => option_value.end)
              end
            end
          when :is, :minimum, :maximum
            raise ArgumentError, ":#{option} must be a nonnegative Integer" unless option_value.is_a?(Integer) and option_value >= 0

            # Declare different validations per option.
            validity_checks = { :is => "==", :minimum => ">=", :maximum => "<=" }

            validates_each(attrs, options) do |record, attr, value|
              value = options[:tokenizer].call(value) if value.kind_of?(String)
              unless !value.nil? and value.size.method(validity_checks[option])[option_value]
                record.errors.add(attr, key, :default => custom_message, :count => option_value)
              end
            end
        end
      end

1Note

Can be used with has_many associations

sjmadsen · Mar 13, 20103 thanks

You can also use this to validate that a has_many association has a specified number of records on the other end:

has_many :members

validates_length_of :members, :minimum => 1

validates_length_of

1Note

Can be used with has_many associations

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