Object-Oriented Programming

Method Stereotypes

Michael L. Collard, Ph.D.

Department of Computer Science, The University of Akron

Method Stereotypes

  • All methods play a role or multiple roles in a class
  • Identifying the role of a method helps with comprehension but also with the original design
  • A method has a primary role, with some methods a secondary role

Method Stereotype Taxonomy

Documentation

  • Method stereotypes can be embedded in the source code as a comment
  • documentation if the identification is manual
  • redocumentation if the identification is automated
  • Useful to be able to update in place

Taxonomy

Stereotype Category Description
Accessors Read access to the state of the object, both direct and derived
Mutators Write access to the state of the object
Creational Methods Create and manage the lifetime of objects
Collaborational Methods Work with objects of other classes
Degenerate Methods No access or changes to state

Accessors

Stereotype Description
get Returns the value of a data member
predicate Returns a Boolean result computed from data members
property Returns information based on data member values
void-accessor Returns information about data members through a parameter

Accessor::get

  • Returns the value of a data member
  • The purpose of the method is very simple and primitive
  • Direct access to the value of the data member
  • C++ Rules:
  • Method is const
  • Returns a data member
  • Return type is primitive or container of a primitive

Accessor::predicate

  • Returns a Boolean result computed from data members
  • Result is not a direct data member but a computation involving data members
  • C++ Rules:
  • Method is const
  • Returns a Boolean value that is not a data member

Accessor::property

  • Returns information based on data member values
  • C++ Rules:
  • Method is const
  • Does not return a data member
  • Return type is primitive or container of primitives
  • Return type is not Boolean

Accessor::void-accessor

  • Returns information about data members through a parameter

Mutators

Stereotype Description
set changes the value of a data member
command executes a complex change of the object’s state
non-void-command command which returns a value

Mutator::set

  • Directly changes the value of a data member
  • The parameter value is stored in the data member
  • C++ Rules:
  • Method is not const
  • Return type is void or Boolean
  • Only one data member is changed

Mutator::command

  • Executes a complex change of the object’s state
  • The change may involve several data members
  • May change the data members either directly or indirectly with another mutator
  • C++ Rules:
  • Method is not const
  • Return type is void or Boolean
  • Complex change to the object’s state is performed, e.g., more than one data member is changed

Mutator::non-void-command

  • Command which returns a value

Collaborational Methods

Stereotype Description
collaborator Works on objects of classes different from itself
controller Works only on objects of classes other than itself

Collaborational::Collaborator

  • Works on objects of classes different from itself
  • C++ Rules:
  • Returns void, and at least one of the method’s parameters or local variables is an object
  • Returns a parameter or local variable that is an object

Collaborational::Controller

  • Works only on objects of classes different from itself

Creational Methods

Stereotype Example/Description
constructor
copy-constructor
destructor
factory Object creation method

Creational::factory

  • Object creation method with the object returned to the client

Degenerate Methods

Stereotype Description
incidental Does not read/change the object state, and no calls to other methods of the same class
stateless Does not read/modify the object state with one call to other methods of the same class
empty Method with no statements

Degenerate::incidental

  • Does not read/change the object state, and no calls to other methods of the same class

Degenerate::stateless

  • Does not read/change the object state with one call to other methods of the same class

Degenerate::empty

  • Method with no statements
  • Typically part of an early implementation
  • Maybe due to functionality moving elsewhere

Clear Design

  • A method should have a single purpose, single responsibility issue
  • Conversely, a method should have a single primary role, i.e., single role issue

Pop or Top vs. Pop and Top

Automated Detection

  • Tool, stereocode, automatically redocuments source code with stereotypes
  • XPath patterns with XPath extension functions
  • Very scalable as it redocuments large systems in minutes