Module: ActiveRecord::Validations

Active Records implement validation by overwriting Base#validate (or the variations, validate_on_create and validate_on_update). Each of these methods can inspect the state of the object, which usually means ensuring that a number of attributes have a certain value (such as not empty, within a given range, matching a certain regular expression).

Example:

  class Person < ActiveRecord::Base
    protected
      def validate
        errors.add_on_empty %w( first_name last_name )
        errors.add("phone_number", "has invalid format") unless phone_number =~ /[0-9]*/
      end

      def validate_on_create # is only run the first time a new object is saved
        unless valid_discount?(membership_discount)
          errors.add("membership_discount", "has expired")
        end
      end

      def validate_on_update
        errors.add_to_base("No changes have occurred") if unchanged_attributes?
      end
  end

  person = Person.new("first_name" => "David", "phone_number" => "what?")
  person.save                         # => false (and doesn't do the save)
  person.errors.empty?                # => false
  person.errors.count                 # => 2
  person.errors.on "last_name"        # => "can't be empty"
  person.errors.on "phone_number"     # => "has invalid format"
  person.errors.each_full { |msg| puts msg }
                                      # => "Last name can't be empty\n" +
                                           "Phone number has invalid format"

  person.attributes = { "last_name" => "Heinemeier", "phone_number" => "555-555" }
  person.save # => true (and person is now saved in the database)

An Errors object is automatically created for every Active Record.

Please do have a look at ActiveRecord::Validations::ClassMethods for a higher level of validations.

Methods

errors run_validations save_with_validation save_with_validation! update_attribute_with_validation_skipping valid? validate validate_on_create validate_on_update validation_block? validation_class?

Classes and Modules

Module ActiveRecord::Validations::ClassMethods

Constants

VALIDATIONS = %w( validate validate_on_create validate_on_update )

Public Instance methods

errors()

Returns the Errors object that holds all information about attribute error messages.

[Source]

# File activerecord/lib/active_record/validations.rb, line 917
    def errors
      @errors ||= Errors.new(self)
    end

save_with_validation(perform_validation = true)

The validation process on save can be skipped by passing false. The regular Base#save method is replaced with this when the validations module is mixed in, which it is by default.

[Source]

# File activerecord/lib/active_record/validations.rb, line 872
    def save_with_validation(perform_validation = true)
      if perform_validation && valid? || !perform_validation
        save_without_validation
      else
        false
      end
    end

save_with_validation!()

Attempts to save the record just like Base#save but will raise a RecordInvalid exception instead of returning false if the record is not valid.

[Source]

# File activerecord/lib/active_record/validations.rb, line 882
    def save_with_validation!
      if valid?
        save_without_validation!
      else
        raise RecordInvalid.new(self)
      end
    end

update_attribute_with_validation_skipping(name, value)

Updates a single attribute and saves the record without going through the normal validation procedure. This is especially useful for boolean flags on existing records. The regular update_attribute method in Base is replaced with this when the validations module is mixed in, which it is by default.

[Source]

# File activerecord/lib/active_record/validations.rb, line 893
    def update_attribute_with_validation_skipping(name, value)
      send(name.to_s + '=', value)
      save(false)
    end

valid?()

Runs validate and validate_on_create or validate_on_update and returns true if no errors were added otherwise false.

[Source]

# File activerecord/lib/active_record/validations.rb, line 899
    def valid?
      errors.clear

      run_validations(:validate)
      validate

      if new_record?
        run_validations(:validate_on_create)
        validate_on_create
      else
        run_validations(:validate_on_update)
        validate_on_update
      end

      errors.empty?
    end

Protected Instance methods

validate(

Overwrite this method for validation checks on all saves and use Errors.add(field, msg) for invalid attributes.

[Source]

# File activerecord/lib/active_record/validations.rb, line 923
      def validate #:doc:
      end

validate_on_create(

Overwrite this method for validation checks used only on creation.

[Source]

# File activerecord/lib/active_record/validations.rb, line 927
      def validate_on_create #:doc:
      end

validate_on_update(

Overwrite this method for validation checks used only on updates.

[Source]

# File activerecord/lib/active_record/validations.rb, line 931
      def validate_on_update # :doc:
      end

Private Instance methods

run_validations(validation_method)

[Source]

# File activerecord/lib/active_record/validations.rb, line 935
      def run_validations(validation_method)
        validations = self.class.read_inheritable_attribute(validation_method.to_sym)
        if validations.nil? then return end
        validations.each do |validation|
          if validation.is_a?(Symbol)
            self.send(validation)
          elsif validation.is_a?(String)
            eval(validation, binding)
          elsif validation_block?(validation)
            validation.call(self)
          elsif validation_class?(validation, validation_method)
            validation.send(validation_method, self)
          else
            raise(
              ActiveRecordError,
              "Validations need to be either a symbol, string (to be eval'ed), proc/method, or " +
              "class implementing a static validation method"
            )
          end
        end
      end

validation_block?(validation)

[Source]

# File activerecord/lib/active_record/validations.rb, line 957
      def validation_block?(validation)
        validation.respond_to?("call") && (validation.arity == 1 || validation.arity == -1)
      end

validation_class?(validation, validation_method)

[Source]

# File activerecord/lib/active_record/validations.rb, line 961
      def validation_class?(validation, validation_method)
        validation.respond_to?(validation_method)
      end