More GRASP Patterns

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Chapter 25

• More GRASP Patterns

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GRASP Patterns

• Creator
• Expert
• Coupling
• Cohesion
• Controller
• Polymorphism
• Indirection
• Pure Fabrication
• Protected Variations

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Polymorphism

• Alternatives based on type
• Use polymorphic operations for related
  alternatives or behaviors
• Do not test for the type of an object and use
  conditional logic to perform different
  alternatives based on type.

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Fig. 25.1
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Fig. 25.2
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Fig. 25.3
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Fig. 25.4
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Fig. 25.5
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Fig. 25.6
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Fig. 25.7
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Pure Fabrication

• When assigning responsibilities to domain classes
  lead to problems with cohesion, coupling, expert,
  or other patterns.
• Use fabricated software classes.
• Example
• Sales class that does DB access for persistent
  storage.
• Better have a PersistentStorage class.
• Entity Javabeans EJB in Java EE.

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Fig. 25.8
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Fig. 25.9
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Indirection

• Using adaptors or intermediaries.
• Decouple two classes, especially when one of them
  is under constant changes.

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Fig. 25.10
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Protected Variations

• Identify points of variations and instability.
• Assign responsibilities to interfaces.