Software Architecture in Practice

4. Principles & Patterns

Design Patterns 

1. Creational patterns - patterns that determine how objects are created 

2. Structural patterns - patterns that dene relationships between objects 

3. Behavioral patterns - patterns that dene the communication between objects

 

Creational Design Patterns 

• Abstract factory - request an object from a factory object 
• Factory method - choosing an object implementation, creating the object and returning it 
• Builder - builds complex objects that may have different representations 
• Dependency injection - request an object from an injector 
• Lazy initialization - create an object only when its needed 
• Object pool - avoid expensive object creation and release of resources by recycling objects that are not in use 
• Prototype - cloning an object to create a new instance 
• Singleton - restrict instantiation from creating more than one object

 

Structural Design Patterns 

• Adapter - adapts one interface to another 
• Bridge - separating an interface from its implementation 
• Composite - structure of different objects 
• Decorator - adds additional functionality to its interface 
• Facade - masks complex structural code eg. using many objects and executes different methods 
• Flyweight - caching and storing objects with the same "value" 
• Private class data - restrict accessor and mutator methods to access 
• Proxy - connects two other components and may add more functionality

 

Behavioral Design Patterns 

• Chain of responsibility - passes a request through a chain of objects 
• Command - encapsulate information to trigger an event or action 
• Interpreter - evaluation of grammatical representation 
• Iterator - a way to access each element of a collection 
• Mediator - coordinates between different objects Memento - restores an object to its previous state 
• Null object - acts as the default value of a class 
• Observer - a way of notifying other objects of an object's state change 
• State - when an internal state changes, the object's behavior changes 
• Strategy - determines the algorithm that should be used for the implementation
• Template method - skeleton of an algorithm as an abstract class that allow subclasses to determine the behavior
• Visitor - separates the algorithm from the object it operates