The Template Method

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The Template Method

• By Sinclair Schuller

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What is the Template Method?

• Skeleton definition of an algorithm
• Allows redefinition of predetermined points
• Preserves structural integrity of algorithm

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Why is it Useful?

• Allows for the factoring out of common behavior
• Presents a clean method for implementing
  algorithms
• Allows for code reuse

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How is it Structured?

• Participants
• Abstract Class
• Concrete Class
• Operations Are
• Hooks
• Or
• Abstract

Diagram http//www.dofactory.com/Patterns/Patter
nTemplate.aspx
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How is it Structured?

• Template method is implemented with calls to
  primitive operations
• Primitive operations either allow full (if
  abstract) or partial (if hook) control to
  subclass
• Keep it simple (minimize number of primitive
  operations)

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Example

• void ShapeDraw()
• InitializeBrush()
• DrawShape() //Here is our hook
• ClearBrush()
• Draw() is the template method

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Example Continued

• void RectangleDrawShape()
• //Rectangle Drawing
• //Implementation
• The Rectangle subclass of Shape overrides
  DrawShape()

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If You Only Remember One Thing

• Template methods provide a means to develop a
  skeleton for an algorithm, making it an ideal and
  necessary method for code reuse.
• Any Questions?

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References

• http//www.dofactory.com/Patterns/PatternTemplate.
  aspx
• Design Patterns Elements of Reusable
  Object-Oriented Software by Gamma, Helm, Johnson
  and Vlissides