Template Methods

Ordering What We DoOrdering What We Do

Example - SolitaireExample - Solitaire

• Initialization of many solitaire games follow this pattern:• Shuffle the cards• Layout the game board• Deal the cards onto the table

• Initialization of many solitaire games follow this pattern:• Shuffle the cards• Layout the game board• Deal the cards onto the table

Options for building two solitaire games

Options for building two solitaire games

• One class per game• One class that defines the overall

structure of a game and sub-classes for each particular game

• One class per game• One class that defines the overall

structure of a game and sub-classes for each particular game

Template for SolitaireTemplate for Solitaire

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Template Method DefinedTemplate Method Defined

• The Template Method Pattern defines the skeleton of an algorithm in a method, deferring some steps to subclasses. It lest subclasses redefine certain steps of an algorithm without changing the algorithm’s structure

• The Template Method Pattern defines the skeleton of an algorithm in a method, deferring some steps to subclasses. It lest subclasses redefine certain steps of an algorithm without changing the algorithm’s structure

Template Method Structure

Template Method Structure

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Types of Methods in a Template

Types of Methods in a Template

• Primitive Operations• Abstract and left to subclasses for definition

• Concrete Operations• Common for all subclasses, so concrete in

the template class

• Hooks• Default implementation in the Template

class, but can be overridden by subclasses• Usually do nothing if not overridden

• Primitive Operations• Abstract and left to subclasses for definition

• Concrete Operations• Common for all subclasses, so concrete in

the template class

• Hooks• Default implementation in the Template

class, but can be overridden by subclasses• Usually do nothing if not overridden

Look at Book’s Barista Example

Look at Book’s Barista Example

Other ExamplesOther Examples

• Equals• Applets• Hooks for init(), start(), stop(), …

• Book’s Pizza Factory

• Equals• Applets• Hooks for init(), start(), stop(), …

• Book’s Pizza Factory