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
Source: show
# File activemodel/lib/active_model/validator.rb, line 107 def self.kind @kind ||= name.split('::').last.underscore.sub(/_validator$/, '').to_sym unless anonymous? end
Accepts options that will be made available through the
options
reader.
Source: show
# File activemodel/lib/active_model/validator.rb, line 112 def initialize(options) @options = options.freeze end
Return the kind for this validator.
Source: show
# File activemodel/lib/active_model/validator.rb, line 117 def kind self.class.kind end
Override this method in subclasses with validation logic, adding errors to
the records errors
array where necessary.
Source: show
# File activemodel/lib/active_model/validator.rb, line 123 def validate(record) raise NotImplementedError, "Subclasses must implement a validate(record) method." end