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Software Design Patterns

Taken from Wikipedia, personal adaptations and additions made, shortened to be used as a small reference card, links back to wikipedia kept for details.

See also Software Anti-Patterns.

Architectural patterns [ Choice: How is the software system (as a whole) organized? ]
Layers Separation of the system in layers, each layer knowing only of the layer above and under itself
PlantUML Graph MVC Separation of the view (user interface) from the model (underlying data) and the controller (user interaction)
PlantUML Graph MVP Model View Presenter: all presentation logic is pushed to the presenter, mainly used for GUI development
PlantUML Graph MVVM Model View ViewModel: The view model handles the view's display logic, is responsible for exposing the data objects from the model in such a way that the objects are easily managed and consumed
Multitier architecture The presentation, the application processing, and the data management are logically separate processes
Pipeline Chain of processing elements
Implicit invocation Event broadcasting, the caller doesn't know who is called
Blackboard system A common knowledge base, is iteratively updated by a diverse subsystems
Peer-to-peer No central server, each peer is supplier and consumer
Service-oriented architecture Loose coupling of services within the system
Naked objects Objects and their representation are not biased by adapters or proxys
Creational patterns [ Choice: How to create the objects? ]
Abstract factory Interface for creating families of related or dependent objects without specifying their concrete classes
Factory method Creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses
Builder Separate the construction of a complex object from its representation. The same construction process can create different representations
Lazy initialization Tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed
Object pool Avoid expensive acquisition and release of resources by recycling objects that are no longer in use
Prototype Specify the kinds of objects to create using a prototypical instance, and create new objects by copying this prototype. (Cloning)
Singleton Ensure a class has only one instance, and provide a global point of access to it
Multiton Ensure a class has only named instances, and provide global point of access to them
Resource acquisition is initialization Ensure that resources are properly released by tying them to the lifespan of suitable objects
Structural patterns [ Choice: What relationship have the objects? ]
Adapter or Wrapper Convert the interface of a class into another interface clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.
Bridge Decouple an abstraction from its implementation so that the two can vary independently
Composite Compose objects into tree structures to represent part-whole hierarchies. Composite lets clients treat individual objects and compositions of objects uniformly
Decorator Attach additional responsibilities to an object dynamically keeping the same interface. Decorators provide a flexible alternative to subclassing for extending functionality
Facade Provide a unified interface to a set of interfaces in a subsystem. Facade defines a higher-level interface that makes the subsystem easier to use
Flyweight Use sharing to support large numbers of fine-grained objects efficiently
Proxy Provide a surrogate or placeholder for another object to control access to it
Behavioral patterns [ Choice: How are the objects communicating? ]
Chain of responsibility Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it
Command Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations
Interpreter Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language
Iterator Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation
Mediator Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently
Restorer An alternative to the existing Memento pattern
Memento Without violating encapsulation, capture and externalize an object's internal state so that the object can be restored to this state later
Null Object Designed to act as a default value of an object, usually to avoid special treatment for null pointers
Observer or Publish/subscribe Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically
Blackboard Generalized observer, which allows multiple readers and writers. Communicates information system-wide
State Allow an object to alter its behavior when its internal state changes. The object will appear to change its class
Strategy Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it
Specification Recombinable business logic in a boolean fashion
Template method Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm's structure
Visitor Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates
Concurrency patterns [ Choice: How to synchronize concurrent access to the object? ]
Active Object Decouples method execution from method invocation that reside in their own thread of control. The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests
Binding Properties Combining multiple observers to force properties in different objects to be synchronized or coordinated in some way
Event-Based Asynchronous Addresses problems with the Asynchronous Pattern that occur in multithreaded programs
Balking Executes an action on an object only when the object is in a particular state
Guarded suspension In concurrent programming, managing operations that require both a lock to be acquired and a precondition to be satisfied before the operation can be executed
Monitor object Approach to synchronize two or more computer tasks that use a shared resource, usually a hardware device or a set of variables
Scheduler Explicitly control when threads may execute single-threaded code
Thread pool A number of threads are created to perform a number of tasks, which are usually organized in a queue. Typically, there are many more tasks than threads
Thread-specific storage Thread-local storage (TLS) is a computer programming method that uses static or global memory local to a thread
Reactor Handling service requests delivered concurrently to a service handler by one or more inputs. The service handler then demultiplexes the incoming requests and dispatches them synchronously to the associated request handlers
Lock One thread puts a “lock” on a resource, preventing other threads from accessing or modifying it
Double checked locking “double-checked locking optimization”. Reduce the overhead of acquiring a lock by first testing the locking criterion (the 'lock hint') in an unsafe manner; only if that succeeds does the actual lock proceed1)
Read write lock Allows concurrent read access to an object but requires exclusive access for write operations
1) In some language/hardware combinations, can be unsafe. It can therefore sometimes be considered an anti-pattern
patterns/patterns.txt · Last modified: 2015/07/25 21:43 by jaap.dehaan