The document outlines several structural design patterns including Adapter, Bridge, Composite, Decorator, Façade, Proxy, and Flyweight. It provides descriptions of what each pattern is, where it would be used, why it would be used, and how it works at a high level. For example, it states that the Adapter pattern enables a noncompliant interface to be used through an intermediary that manages an adaptation process to effect compliance. It is used when needing to integrate with a noncompliant interface or leverage another design's functionality. An intermediary class maps the desired functionality to the required target.

1. Design Pattern
By Julie Iskander
MSc. Communication and Electronics

2. Outlines
Lecture 3
• Structural Design Patterns
• Adapter
• Bridge
• Composite
• Decorator
• Façade
• Proxy
• Flyweight

3. Structural Patterns

4. adapter DP
(Class-Structural DP)

5. adapter DP
(Class-Structural DP)

6. adapter DP
(Class-Structural DP)
• Adapter in OO

7. adapter DP
(Class-Structural DP)
• What
• A design that enables a noncompliant interface to be used
through an intermediary, which manages an adaptation
process to effect compliance.
• Where
• A requirement to integrate with a noncompliant interface or a
requirement for one design to leverage the functionality of
another design.
• Why
• To reuse or integrate existing functionality, or adapt to change
in business requirements that necessitates reengineering
design or functionality.
• How
• An intermediary class is used to map the desired functionality
from the source interface to that required by the target

8. adapter DP
(Object-Structural DP)

9. adapter DP
(Class-Structural DP)

10. adapter DP
(Object-Structural DP)

11. Bridge DP
(Object – Structural DP)
• What
• Decouple an abstraction from its implementation so that
the two can vary independently.
• Avoid a permanent binding between an abstraction and
its implementation or to hide implementation from client
• Why
• Decoupling interface and implementation.
• How
• Abstraction forwards client requests to its Implementor
object.

12. Bridge DP
(Object – Structural DP)

13. Bridge DP
(Object – Structural DP)

14. Bridge DP
(Object – Structural DP)

15. • Example
• A bank Account may be a saving or a current
account. A bank account may also be a
student account or a child account or a
normal account
• Note that:
• Abstract Factory can create a particular
Bridge
• Assignment: Show how can this be
done?
Bridge DP
(Object – Structural DP)

16. Bridge Vs. Adapter
• Bridge DP:
• Meant to separate an interface from its
implementation, to vary easily and
independently
• Adapter DP:
• Meant to change the interface of an existing
object
• It is applied to systems after they’re designed.
• Makes unrelated classes work together.

17. Composite DP
(Object – Structural DP)
• What
• A design that ensures that an entity and a composite of
entities expose the same interface.
• Where
• A requirement to treat simple and composite objects alike
• Why
• To organize entities into hierarchies, that contain single
entities and composite entities
• How
• A common interface is inherited by a composite and an
entity

18. Composite DP
(Object – Structural DP)

19. Composite DP
(Object – Structural DP)

20. A parent class should
define operations that
are meaningful to all
subclass
Composite DP
(Object – Structural DP)

21. decorator DP
(Object – Structural DP)

22. decorator DP
(Object – Structural DP)

23. decorator DP
(Object – Structural DP)

24. decorator DP
(Object – Structural DP)

25. decorator DP
(Object – Structural DP)

26. decorator DP
(Object – Structural DP)
• What
• Attach additional responsibilities to an object
dynamically.
• Where
• To add responsibilities to individual objects dynamically,
without affecting other objects.
• For responsibilities that can be withdrawn.
• Why
• Add optional responsibilities
• How
• Abstraction forwards client requests to its Implementor

27. decorator DP
(Object – Structural DP)

28. decorator DP
(Object – Structural DP)

29. decorator DP
(Object – Structural DP)

30. decorator DP
(Object – Structural DP)

31. decorator DP
(Object – Structural DP)

32. decorator DP
(Object – Structural DP)

33. • Decorator & Adapter:
• A decorator changes an object responsibility
while an adapter changes its interface
• Decorator & Composite:
• A decorator adds responsibility while a
composite is intended for object aggregation
decorator DP
(Object – Structural DP)

34. Façade DP
(Object – structural dp)
• What
• A design to hide the complexity of many interface behind
a simple and uniform interface.
• A requirement for a high-level abstraction that is simple
to use.
• Why
• Software becomes complex as it seeks to interact with
many interfaces, systems, or subsystems.
• How
• Managing multiple interfaces is delegated to a facade
class that hides the complexity and presents a simple
interface.

35. Façade DP
(Object – structural dp)

37. Façade DP
(Object – structural dp)

38. Proxy DP
(Object – structural dp)
• What
• Represents or regulates access to an object that is scarce or remote.
Provide a surrogate or placeholder for another object to control
access to it.
• Where
• Access needed to be regulated or access to a principal needs to be
distributed.
• Why
• To regulate client code access to a given resource; or for remote
access to functionality.
• How
• A proxy class is derived from the same base class as the principal
class. The proxy class uses composition—it creates a member
instance of the principal—to expose the functionality of the principal
through a set of wrapper methods or properties. The client code
creates an instance of the proxy class that regulates or distributes
access to the functionality of the principal.

39. Proxy DP
(Object – structural dp)

40. Proxy DP
(Object – structural dp)

41. Report #2:
Flyweight DP
N.B. Hand Written 