Key Relationships

• Strategy - Template Method - Subclassing
  • Strategy provides a way
    to change the algorithm/behavior of an object at run-time.
  • Template Method provides a way
    to change certain parts of the algorithm/behavior of a class at compile-time.
  • Subclassing is the standard way
    to change the algorithm/behavior of a class at compile-time.
• Strategy - Abstract Factory
  • Strategy
    A class delegates performing an algorithm to a strategy object.
  • Abstract Factory
    A class delegates creating an object to a factory object.
• Strategy - Abstract Factory - Dependency Injection
  • Strategy
    A class can be configured with a strategy object.
  • Abstract Factory
    A class can be configured with a factory object.
  • Dependency Injection
    Actually performs the configuration by creating and injecting the objects a class requires.
• Strategy - Decorator
  • Strategy provides a way
    to exchange the algorithm of an object at run-time.
    This is done from inside the object.
    The object is designed to delegate an algorithm to a Strategy object.
    
  • Decorator provides a way
    to extend the functionality of an object at run-time.
    This is done from outside the object.
    The object already exists and isn't needed to be touched. That's very powerful.
    
• Strategy - Command
  • Strategy provides a way
    to configure an object with an algorithm at run-time
    instead of committing to an algorithm at compile-time.
  • Command provides a way
    to configure an object with a request at run-time
    instead of committing to a request at compile-time.