Template What!?

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Template What ?!
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The Template Method

• The Point
• To implement invariant parts of an algorithm once
  then let the subclasses implement the behavior
  that can vary.
• How this is done
• The template method contains the skeleton of an
  algorithm, allowing subclasses to carry out
  specific steps.
• This is done without changing the algorithms
  structure.

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When to Use Template Method

• When there is common behavior among subclasses
  that should be localized in one class to prevent
  code duplication.
• Template methods are a fundamental technique for
  code re-use.
• To direct subclass extensions.

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Trivial Example
Bulldog eat() nap() bark() walkBull()
Greyhound eat() nap() bark() walkGrey()
Rottweiler eat() nap() bark() walkRott()
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Trivial Example
Bulldog lumbers()
Greyhound prances()
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Slightly Less Trivial Example
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Slightly Less Trivial Example
Jason litigation()
Pam patents()
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Results of the Template Method

• Code reusability, that is, the subclass reuses
  the code of the base class.
• Prevents duplication of common behaviors
  (especially important in class libraries).
• Leads to inverted control structure where the
  parent class calls the operations of a subclass.

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Any Questions ?