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[:base] << "This is some custom error message"
record.errors[: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(record, 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[attribute] << 'must be Mr. Mrs. or Dr.' unless ['Mr.', 'Mrs.', 'Dr.'].include?(value)
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, :title => true end
Validator may also define a setup instance method which will get called with the class that using that validator as it's 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.
Returns the kind of the validator.
PresenceValidator.kind # => :presence UniquenessValidator.kind # => :uniqueness
# File lib/active_model/validator.rb, line 108 def self.kind @kind ||= name.split('::').last.underscore.sub(/_validator$/, '').to_sym unless anonymous? end
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