module ActiveModel
module ActiveModel::AttributeMethods
module ActiveModel::AttributeMethods::ClassMethods
module ActiveModel::Callbacks
module ActiveModel::Conversion
module ActiveModel::DeprecatedErrorMethods
module ActiveModel::Dirty
module ActiveModel::Lint
module ActiveModel::Lint::Tests
module ActiveModel::MassAssignmentSecurity
module ActiveModel::MassAssignmentSecurity::ClassMethods
module ActiveModel::MassAssignmentSecurity::Sanitizer
module ActiveModel::Naming
module ActiveModel::Observing
module ActiveModel::Observing::ClassMethods
module ActiveModel::Serialization
module ActiveModel::Serializers
module ActiveModel::Serializers::JSON
module ActiveModel::Serializers::Xml
module ActiveModel::Translation
module ActiveModel::VERSION
module ActiveModel::Validations
module ActiveModel::Validations::Callbacks
module ActiveModel::Validations::Callbacks::ClassMethods
module ActiveModel::Validations::ClassMethods
module ActiveModel::Validations::HelperMethods
class ActiveModel::AttributeMethods::ClassMethods::AttributeMethodMatcher
class ActiveModel::BlockValidator
class ActiveModel::EachValidator
class ActiveModel::Errors
class ActiveModel::MassAssignmentSecurity::BlackList
class ActiveModel::MassAssignmentSecurity::PermissionSet
class ActiveModel::MassAssignmentSecurity::WhiteList
class ActiveModel::MissingAttributeError
class ActiveModel::Name
class ActiveModel::Observer
class ActiveModel::Serializers::Xml::Serializer
class ActiveModel::Serializers::Xml::Serializer::Attribute
class ActiveModel::Serializers::Xml::Serializer::MethodAttribute
class ActiveModel::TestCase
class ActiveModel::Validations::AcceptanceValidator
class ActiveModel::Validations::ConfirmationValidator
class ActiveModel::Validations::ExclusionValidator
class ActiveModel::Validations::FormatValidator
class ActiveModel::Validations::InclusionValidator
class ActiveModel::Validations::LengthValidator
class ActiveModel::Validations::NumericalityValidator
class ActiveModel::Validations::PresenceValidator
class ActiveModel::Validator
activemodel
3.0.20
# add_observer!
def add_observer!(klass) #:nodoc: klass.add_observer(self) end