What is the difference between the Template patterns and the Strategy pattern?

The Template Pattern and the Strategy Pattern are both behavioral design patterns, but they have different focuses and intents. Here’s a breakdown of the differences between these patterns:

  1. Template Pattern:
  • Purpose: The Template Pattern defines the skeleton of an algorithm in a base class, allowing subclasses to override specific steps of the algorithm while preserving the overall structure. It provides a common structure for a family of algorithms but allows subclasses to customize certain steps as needed.
  • Usage: The Template Pattern is used when you want to define a common algorithm or process but allow different variations or implementations of certain steps. It promotes code reuse and encapsulates the common parts of an algorithm in a base class while allowing customization in derived classes.
  • Interaction: In the Template Pattern, the base class (also known as the template class) defines the overall algorithm structure and provides default implementations for some or all of the steps. Subclasses (also known as concrete implementations) can override specific steps to provide their own implementations.
  1. Strategy Pattern:
  • Purpose: The Strategy Pattern enables the definition of a family of interchangeable algorithms or strategies and encapsulates each strategy into its own class. It allows clients to dynamically select or switch between different algorithms at runtime.
  • Usage: The Strategy Pattern is used when you want to provide multiple algorithms or strategies that can be used interchangeably, depending on the context or specific requirements. It allows for easy substitution of one strategy with another without impacting the client code.
  • Interaction: In the Strategy Pattern, the client code holds a reference to an interface or base class representing the strategy. The client can dynamically select or set a specific strategy implementation, and the selected strategy is used to perform a specific operation or behavior.

Key Differences:

  1. Intent: The Template Pattern focuses on defining a common algorithm with customizable steps, allowing subclasses to override certain steps while maintaining the overall structure. The Strategy Pattern focuses on encapsulating interchangeable algorithms or strategies and allowing clients to select or switch between them.
  2. Customization vs. Substitution: The Template Pattern allows subclasses to customize or override specific steps of an algorithm while keeping the overall structure intact. The Strategy Pattern enables dynamic selection and substitution of different algorithms or strategies at runtime.
  3. Inheritance vs. Composition: The Template Pattern uses inheritance to define the common structure and variations of an algorithm. The Strategy Pattern uses composition, where the client holds a reference to a specific strategy implementation.
  4. Static vs. Dynamic Behavior: The Template Pattern focuses on static behavior, as the structure of the algorithm is determined at compile-time. The Strategy Pattern provides dynamic behavior, as the client can select or switch between different strategies at runtime.

In summary, the Template Pattern defines a common algorithm with customizable steps, allowing subclasses to override specific steps. The Strategy Pattern encapsulates interchangeable algorithms as separate classes, allowing clients to dynamically select or switch between them. The Template Pattern focuses on structuring algorithms, while the Strategy Pattern focuses on providing alternative strategies. The choice between them depends on the specific requirements and goals of your application.

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