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Template Method

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Edwin Dalorzo edited this page Jan 27, 2018 · 1 revision

Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.

Required Readings

Questions

  • What is the intent of the template method pattern?
  • What is the difference between an strategy pattern and a template method pattern?
  • How could the template method pattern be combined with a strategy pattern?
  • The Gang of Four calls this a “template method.” Why do they do this?
  • According to the Gang of Four, the intent of the template method pattern is to “define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Redefine the steps in an algorithm without changing the algorithm’s structure.” What does this mean?
  • How is the principle of "encapsulate what varies" implemented in the template method pattern?
  • What is the Hollywood Principle? How does the template method implements it?
  • What is the importance of minimizing the number of primitive operations extending classes must implement?
  • What is a hook method and what are they used for?
  • How do we know when to use hooks and when to use abstract methods?
  • How can we avoid that the template method be overridden?
  • How does the template method can be designed for inheritance as suggested by Bloch in Effective Java?
  • How do we know when to use abstract methods and when to use hooks?
  • How does the template method provides reusability through inheritance?
  • What can we do in terms of naming conventions to make clearer which operations need overriding?
  • How does the template method fosters cohesion?
  • What are the template method coupling points?
  • How does the template method fosters the open/closed principle?
  • The Template Method relies on inheritance. Would it be possible to get the same functionality of a Template Method, using object composition? What would some of the tradeoffs be?
  • How does the Hollywood Principle relate to the Dependency Inversion Principle?
  • Take a design that has a lot of lower- and higher-level components (see page 298 in HFDP). Now apply the Hollywood principle and clean up the design as a group.
  • Lead a group discussion on the first Brain Power on page 305 in Head First. Pick apart the implementation of Sun’s sort(), which uses static methods instead of inheritance. Did they do the right thing? Split into smaller groups if you like, and then come back together to discuss or debate as a large group.

Optional Readings

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