Design Pattern

1
Design Pattern Bridge(Structural)

• References
• Yih-shoung Chen, Department of Information
  Engineering, Feng Chia University,Taiwan, R.O.C.
• The Bridge Pattern, SENG 609.04 Design Patterns,
  University of Calgary
• The Bridge Pattern, CpSc 872 Software Engineering
  
• Gamma, E., R. Helm, R. Johnson, J. Vlissides.
  Design Patterns Elements of Reusable
  Object-Oriented Software.

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Intent

• Decouple an abstraction from its implementation
  so that the two can vary independently
• Allows different implementations of an interface
  to be decided upon dynamically.
• Also known as Handle/Body pattern

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Motivation Applicability

• Avoid a permanent binding between an abstraction
  and its implementation
• Both the abstractions and their implementation
  should be extensible by subclassing
• Changes in the implementation of an abstraction
  do not impact the clients
• Share an implementation among multi objects and
  this facts should be hidden from the client
• E.g. Windows

4
Participants

• Abstraction
• Refined abstraction
• Concrete implementor
• Implementor

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Structure
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Example of problem suitable for bridge
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A more complex situation
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Solution using Bridge
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Pros Cons

• Pros
• decoupling of the implementation from the
  interface
• improved extensibility of classes
• additional capability for hiding implementation
  details from clients
• best leveraged as a pure design-time pattern
• Cons (Implementation Issues)
• abstractions that have only one implementation
• creating the right Implementor
• sharing implementors
• use of multiple inheritance

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Adapter vs Bridge

• Similarities
• Both used to hide the details of the underlying
  implementation.
• Difference
• The adapter pattern is geared towards making
  unrelated components work together
• Applied to systems after theyre designed
  (reengineering, interface engineering).
• A bridge, on the other hand, is used up-front in
  a design to let abstractions and implementations
  vary independently.
• Green field engineering of an extensible system
  
• New beasts can be added to the object zoo,
  even if these are not known at analysis or system
  design time.
• Structural difference Bridge can abstract a
  complex entity from its implementation Adapter
  only abstracts a single interface

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Thank You