Wish list and OOP-principles ●●
loose coupling: 1 change = ceteris paribus ●● code reuse (is not the same as copy/paste) ●● open for extension, closed for modification ●● encapsulate what varies ●● single responsibility principle ●● program against an interface not against an imple- mentation. Dependency injection ●● prefer composition over inheritance (in fact this is all the same with different words)
Creational design patterns ●● Factory
Method: Allow subclasses to “decide” which class to instantiate. ●● Abstract Factory: Encapsulate a set of analo- gous factories that produce families of objects. ●● Builder: Encapsulate the construction of com- plex objects from their representation; so, the same building process can create various repre- sentations by specifying only type and content. ●● Singleton: Ensure that only a single instance of a class exists and provide a single method for gaining access to it. ●● Prototype: Create an initialized instance for cloning or copying.
Joomla! ●● JFactory: a class
with static methods to instantiate objects like JDatabase, JUser, JDocument, JTemplate, etc. ●● most of those methods are singletons Nooku ●● KFactory: any class can be instantiated ●● get() = singleton, tmp() = any instantiation
Structural design patterns ●● Adapter:
Adapt an interface to an expected interface. ●● Bridge: Decouple an interface from its implementation. ●● Composite: Create a tree structure for part-whole hierarchies. ●● Decorator: Extend functionality dynamically. ●● Facade: Simplify usage by defining a high-level interface. ●● Flyweight: Support fine-grained objects efficiently by sharing. ●● Proxy: Represent an object with another object for access control.
Joomla! ●● new in 1.6:
JAdapter and JAdapterInstance ●● JUpdateAdapter extends JAdapterInstance JUpdaterExtension & JUpdaterExtension extend JUpdateAdapter wanted: documentation and examples! what does it adapt?
Behavioral design patterns ●● Chain
of Responsibility: Define a method of passing a request among a chain of objects. ●● Command: Encapsulate a command request in an object. ●● Interpreter: Allow inclusion of language elements in an appli- cation. ●● Iterator: Enable sequential access to collection elements. ●● Mediator: Define simplified communication between classes. ●● Memento: Save and restore the internal state of an object. ●● Observer: Define a scheme for notifying objects of changes to another object. ●● State: Alter the behavior of an object when its state changes. ●● Strategy: Encapsulate an algorithm inside a class. ●● Template Method: Allow subclasses to redefine the steps of an algorithm. ●● Visitor: Define a new operation on a class without changing it.
Nooku ●● KCommandChain + KCommandContext,
KCommandEvent, KCommandHandler and KCommandInterface ●● N.B.: executes a series of commands instead of passing a command to a series of handlers (like in Tapestry e.g.) ...correct me if I’m wrong....
Visitor Make a kind of
plugin-possibility for methods: in that way me- thods can be added in runtime. printservice! c
extra: Mixin ●● Used in
Nooku (and a.o. in Ruby and Python) ●● a kind of abstract class that is mixed into another object ●● all methods of the mixin are now part of the object ●● handle with care: beware of tight coupling....
Golden OO-principles ●● encapsulate what
varies, OCP ●● 1class, 1 responsibility, SRP ●● program against an interface, not against an imple- mentation, DIP ●● prefer composition over inheritance ●● loose coupling, modular black boxes