Design Problems

• Extending Functionality at Run-Time
  • How can responsibilities be added to (and withdrawn from) an object dynamically?
  • How can the functionality of an object be extended at run-time?
  • How can a simple class be defined that is extended at run-time
    instead of implementing all foreseeable functionality in a complex class?
• Flexible Alternative to Subclassing
  • How can a flexible alternative be provided to subclassing
    for extending the functionality of a class at compile-time?

Refactoring Problems

• Inflexible Code
  • How can classes that include hard-wired extensions (compile-time implementation dependencies) be refactored? Move Embellishment to Decorator (144) [JK05]