method

validate

v7.1.3.2 - Show latest stable - Class: ActiveModel::Validations::ClassMethods

validate(*args, &block)

public

Adds a validation method or block to the class. This is useful when overriding the validate instance method becomes too unwieldy and you’re looking for more descriptive declaration of your validations.

This can be done with a symbol pointing to a method:

class Comment
  include ActiveModel::Validations

  validate :must_be_friends

  def must_be_friends
    errors.add(:base, 'Must be friends to leave a comment') unless commenter.friend_of?(commentee)
  end
end

With a block which is passed with the current record to be validated:

class Comment
  include ActiveModel::Validations

  validate do |comment|
    comment.must_be_friends
  end

  def must_be_friends
    errors.add(:base, 'Must be friends to leave a comment') unless commenter.friend_of?(commentee)
  end
end

Or with a block where self points to the current record to be validated:

class Comment
  include ActiveModel::Validations

  validate do
    errors.add(:base, 'Must be friends to leave a comment') unless commenter.friend_of?(commentee)
  end
end

Note that the return value of validation methods is not relevant. It’s not possible to halt the validate callback chain.

Options:

:on - Specifies the contexts where this validation is active. Runs in all validation contexts by default nil. You can pass a symbol or an array of symbols. (e.g. on: :create or on: :custom_validation_context or on: [:create, :custom_validation_context])
: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.

NOTE: Calling validate multiple times on the same method will overwrite previous definitions.

# File activemodel/lib/active_model/validations.rb, line 171
      def validate(*args, &block)
        options = args.extract_options!

        if args.all?(Symbol)
          options.each_key do |k|
            unless VALID_OPTIONS_FOR_VALIDATE.include?(k)
              raise ArgumentError.new("Unknown key: #{k.inspect}. Valid keys are: #{VALID_OPTIONS_FOR_VALIDATE.map(&:inspect).join(', ')}. Perhaps you meant to call `validates` instead of `validate`?")
            end
          end
        end

        if options.key?(:on)
          options = options.merge(if: [predicate_for_validation_context(options[:on]), *options[:if]])
        end

        set_callback(:validate, *args, options, &block)
      end

      # List all validators that are being used to validate the model using
      # +validates_with+ method.
      #
      #   class Person
      #     include ActiveModel::Validations
      #
      #     validates_with MyValidator
      #     validates_with OtherValidator, on: :create
      #     validates_with StrictValidator, strict: true
      #   end
      #
      #   Person.validators
      #   # => [
      #   #      #<MyValidator:0x007fbff403e808 @options={}>,
      #   #      #<OtherValidator:0x007fbff403d930 @options={on: :create}>,
      #   #      #<StrictValidator:0x007fbff3204a30 @options={strict:true}>
      #   #    ]
      def validators
        _validators.values.flatten.uniq
      end

      # Clears all of the validators and validations.
      #
      # Note that this will clear anything that is being used to validate
      # the model for both the +validates_with+ and +validate+ methods.
      # It clears the validators that are created with an invocation of
      # +validates_with+ and the callbacks that are set by an invocation
      # of +validate+.
      #
      #   class Person
      #     include ActiveModel::Validations
      #
      #     validates_with MyValidator
      #     validates_with OtherValidator, on: :create
      #     validates_with StrictValidator, strict: true
      #     validate :cannot_be_robot
      #
      #     def cannot_be_robot
      #       errors.add(:base, 'A person cannot be a robot') if person_is_robot
      #     end
      #   end
      #
      #   Person.validators
      #   # => [
      #   #      #<MyValidator:0x007fbff403e808 @options={}>,
      #   #      #<OtherValidator:0x007fbff403d930 @options={on: :create}>,
      #   #      #<StrictValidator:0x007fbff3204a30 @options={strict:true}>
      #   #    ]
      #
      # If one runs <tt>Person.clear_validators!</tt> and then checks to see what
      # validators this class has, you would obtain:
      #
      #   Person.validators # => []
      #
      # Also, the callback set by <tt>validate :cannot_be_robot</tt> will be erased
      # so that:
      #
      #   Person._validate_callbacks.empty?  # => true
      #
      def clear_validators!
        reset_callbacks(:validate)
        _validators.clear
      end

      # List all validators that are being used to validate a specific attribute.
      #
      #   class Person
      #     include ActiveModel::Validations
      #
      #     attr_accessor :name, :age
      #
      #     validates_presence_of :name
      #     validates_inclusion_of :age, in: 0..99
      #   end
      #
      #   Person.validators_on(:name)
      #   # => [
      #   #       #<ActiveModel::Validations::PresenceValidator:0x007fe604914e60 @attributes=[:name], @options={}>,
      #   #    ]
      def validators_on(*attributes)
        attributes.flat_map do |attribute|
          _validators[attribute.to_sym]
        end
      end

      # Returns +true+ if +attribute+ is an attribute method, +false+ otherwise.
      #
      #  class Person
      #    include ActiveModel::Validations
      #
      #    attr_accessor :name
      #  end
      #
      #  User.attribute_method?(:name) # => true
      #  User.attribute_method?(:age)  # => false
      def attribute_method?(attribute)
        method_defined?(attribute)
      end

      # Copy validators on inheritance.
      def inherited(base) # :nodoc:
        dup = _validators.dup
        base._validators = dup.each { |k, v| dup[k] = v.dup }
        super
      end

      private
        @@predicates_for_validation_contexts = {}

        def predicate_for_validation_context(context)
          context = context.is_a?(Array) ? context.sort : Array(context)

          @@predicates_for_validation_contexts[context] ||= -> (model) do
            if model.validation_context.is_a?(Array)
              model.validation_context.any? { |model_context| context.include?(model_context) }
            else
              context.include?(model.validation_context)
            end
          end
        end
    end

2Notes

Typo in example above

nhance · Jun 28, 2011

You aren't mistaken. That is an error in the example with the block above. There's an extra '(' character.

Accepted parameters for validate

ggarnier · May 28, 2012

Validate method also accepts +:on+ and +:if+ parameters. The default value for +:on+ is +:save+, the other accepted values are +:create+ and +:update+

class Comment
include ActiveModel::Validations

validate :must_be_friends, :on => :create, :if => Proc.new {|comment| some_condition}

def must_be_friends
  errors.add(:base, "Must be friends to leave a comment") unless commenter.friend_of?(commentee)
end
end

validate

2Notes

Typo in example above

Accepted parameters for validate

Related methods