Module | ActiveRecord::Validations
In: | lib/active_record/validations.rb

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 save_with_validation save_with_validation! update_attribute_with_validation_skipping valid? validate validate_on_create validate_on_update

### 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.

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.

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.

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.

valid?()

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

### Protected Instance methods

validate(

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

validate_on_create(

Overwrite this method for validation checks used only on creation.

validate_on_update(

Overwrite this method for validation checks used only on updates.

[Validate]