Active Model Validator
A simple base class that can be used along with ActiveModel::Validations::ClassMethods#validates_with
class Person include ActiveModel::Validations validates_with MyValidator end class MyValidator < ActiveModel::Validator def validate(record) if some_complex_logic record.errors[:base] = "This record is invalid" end end private def some_complex_logic # ... end end
Any class that inherits from ActiveModel::Validator must implement a method
called validate
which accepts a record
.
class Person include ActiveModel::Validations validates_with MyValidator end class MyValidator < ActiveModel::Validator def validate(record) record # => The person instance being validated options # => Any non-standard options passed to validates_with end end
To cause a validation error, you must add to the record
's
errors directly from within the validators message
class MyValidator < ActiveModel::Validator def validate(record) record.errors.add :base, "This is some custom error message" record.errors.add :first_name, "This is some complex validation" # etc... end end
To add behavior to the initialize method, use the following signature:
class MyValidator < ActiveModel::Validator def initialize(options) super @my_custom_field = options[:field_name] || :first_name end end
The easiest way to add custom validators for validating individual
attributes is with the convenient ActiveModel::EachValidator
.
For example:
class TitleValidator < ActiveModel::EachValidator def validate_each(record, attribute, value) record.errors.add attribute, 'must be Mr. Mrs. or Dr.' unless value.in?(['Mr.', 'Mrs.', 'Dr.']) end end
This can now be used in combination with the validates
method
(see ActiveModel::Validations::ClassMethods.validates
for more
on this)
class Person include ActiveModel::Validations attr_accessor :title validates :title, :presence => true end
Validator may also define a setup
instance method which will get called with the class that using that
validator as its argument. This can be useful when there are prerequisites
such as an attr_accessor
being present for example:
class MyValidator < ActiveModel::Validator def setup(klass) klass.send :attr_accessor, :custom_attribute end end
This setup method is only called when used with validation macros or the
class level validates_with
method.
[R] | options |
Returns the kind of the validator. Examples:
PresenceValidator.kind # => :presence UniquenessValidator.kind # => :uniqueness
Accepts options that will be made available through the
options
reader.
Return the kind for this validator.
Override this method in subclasses with validation logic, adding errors to
the records errors
array where necessary.