Template Method Pattern

The Template Method Pattern is a behavioral design pattern that defines the skeleton of an algorithm in a method, deferring some steps to subclasses. It lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.

Template Method Pattern: A design pattern that provides a template for an algorithm, allowing subclasses to override specific steps while keeping the overall structure intact.

The Template Method Pattern typically consists of:

• Abstract Class: Contains the template method and defines the invariant parts of the algorithm.
• Concrete Classes: Implement the specific steps defined by the abstract class.

Here is a basic implementation of the Template Method Pattern in Python:

class CoffeeTemplate:
    def prepare_coffee(self):
        self.boil_water()
        self.brew()
        self.pour_in_cup()
        self.add_condiments()

    def boil_water(self):
        print("Boiling water")

    def pour_in_cup(self):
        print("Pouring into cup")

    def add_condiments(self):
        pass  # To be implemented by subclasses

class Tea(CoffeeTemplate):
    def brew(self):
        print("Steeping the tea")

    def add_condiments(self):
        print("Adding lemon")

class Coffee(CoffeeTemplate):
    def brew(self):
        print("Dripping coffee through filter")

    def add_condiments(self):
        print("Adding sugar and milk")

# Usage
tea = Tea()
tea.prepare_coffee()

coffee = Coffee()
coffee.prepare_coffee()

Template Method Pattern is particularly useful in the following scenarios:

• When you have multiple classes that share a common algorithm but differ in specific steps.
• When you want to control the overall structure of an algorithm while allowing flexibility in its implementation.
• When you want to promote code reuse and reduce code duplication across similar classes.

When implementing the Template Method Pattern, consider the following best practices:

• Keep the template method public and final to prevent subclasses from modifying it.
• Encapsulate the variant parts in the subclass to ensure the algorithm remains stable.
• Clearly document the template method and its steps for better maintainability.