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Four Design Patterns - Coggle Diagram
Four Design Patterns
Structural Patterns
Decorator
used to extend or alter the functionality of objects at run-time by wrapping them in an object of a decorator class. This provides a flexible alternative to using inheritance to modify behaviour.
Facade
- used to provide a surrogate or placeholder object, which references an underlying object.
- The proxy provides the same public interface as the underlying subject class, adding a level of indirection by accepting requests from a client object and passing these to the real subject object as necessary.
Composite
used to create hierarchical, recursive tree structures of related objects where any element of the structure may be accessed and utilised in a standard manner.
Flyweight
to reduce the memory and resource usage for complex models containing many hundreds, thousands or hundreds of thousands of similar objects.
Bridge
used to separate the abstract elements of a class from the implementation details, providing the means to replace the implementation details without modifying the abstraction.
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Adapter
used to provide a link between two otherwise incompatible types by wrapping the "adaptee" with a class that supports the interface required by the client.
Creational Patterns
Factory Method
to replace class constructors, abstracting the process of object generation so that the type of the object instantiated can be determined at run-time.
Prototype
used to instantiate a new object by copying all of the properties of an existing object, creating an independent clone. This practise is particularly useful when the construction of a new object is inefficient.
Builder
used to create complex objects with constituent parts that must be created in the same order or using a specific algorithm. An external class controls the construction algorithm.
Singleton
ensures that only one object of a particular class is ever created. All further references to objects of the singleton class refer to the same underlying instance.
Abstract Factory
used to provide a client with a set of related or dependant objects. The "family" of objects created by the factory are determined at run-time.
Behavioural Patterns
Memeto
used to capture the current state of an object and store it in such a manner that it can be restored at a later time without breaking the rules of encapsulation.
Obeserver
used to allow an object to publish changes to its state. Other objects subscribe to be immediately notified of any changes.
Mediator
used to reduce coupling between classes that communicate with each other. Instead of classes communicating directly, and thus requiring knowledge of their implementation, the classes send messages via a mediator object.
State
alter the behaviour of an object as its internal state changes. The pattern allows the class for an object to apparently change at run-time
Iterator
to provide a standard interface for traversing a collection of items in an aggregate object without the need to understand its underlying structure.
Strategy
used to create an interchangeable family of algorithms from which the required process is chosen at run-time.
Interpreter
to define the grammar for instructions that form part of a language or notation, whilst allowing the grammar to be easily extended.
Template Method
used to define the basic steps of an algorithm and allow the implementation of the individual steps to be changed.
Command
used to express a request, including the call to be made and all of its required parameters, in a command object. The command may then be executed immediately or held for later use.
Visitor
used to separate a relatively complex set of structured data classes from the functionality that may be performed upon the data that they hold.
Chain of Responsibility
used to process varied requests, each of which may be dealt with by a different handler.