Template Method Pattern: Defining Algorithms with Reusable Steps

Have you ever encountered a scenario where different parts of your application require similar processing logic but with slight variations? Instead of duplicating code, the Template Method Pattern provides a structured approach to defining algorithms with reusable steps, allowing subclasses to customize specific parts. This pattern promotes code reuse and maintains a clear workflow while enabling flexibility in implementation.

In this article, we will explore the Template Method Pattern in detail, discuss its advantages, and implement it in .NET with a practical example.

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What is the Template Method Pattern?

The Template Method Pattern is a behavioral design pattern that defines the skeleton of an algorithm in a base class and allows subclasses to implement specific steps. It helps enforce a consistent structure while letting derived classes provide their own behavior for particular steps.

Key Characteristics:

• Defines an algorithm’s structure in a base class.
• Allows subclasses to override specific steps without changing the algorithm.
• Promotes code reuse and maintainability.
• Reduces duplication by enforcing a common template.

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Real-World Example: Coffee Brewing Process

Consider a coffee-making machine. The steps to brew coffee are:

1. Boil water.
2. Brew coffee.
3. Pour coffee into a cup.
4. Add condiments (optional).

Most coffee-making processes follow this pattern, but variations exist (e.g., black coffee vs. cappuccino). The Template Method Pattern is ideal for structuring such workflows.

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Implementing the Template Method Pattern in .NET

Let's implement this pattern in C# using an example of making different types of beverages.

Step 1: Define the Abstract Class (Template)

public abstract class Beverage
{
    // Template method defining the algorithm
    public void PrepareBeverage()
    {
        BoilWater();
        Brew();
        PourInCup();
        AddCondiments();
    }

    protected void BoilWater()
    {
        Console.WriteLine("Boiling water...");
    }

    protected abstract void Brew();
    
    protected void PourInCup()
    {
        Console.WriteLine("Pouring into cup...");
    }

    protected abstract void AddCondiments();
}

Step 2: Create Concrete Implementations

Coffee Class

public class Coffee : Beverage
{
    protected override void Brew()
    {
        Console.WriteLine("Brewing coffee...");
    }

    protected override void AddCondiments()
    {
        Console.WriteLine("Adding sugar and milk...");
    }
}

Tea Class

public class Tea : Beverage
{
    protected override void Brew()
    {
        Console.WriteLine("Steeping the tea...");
    }

    protected override void AddCondiments()
    {
        Console.WriteLine("Adding lemon...");
    }
}

Step 3: Using the Template Method Pattern

class Program
{
    static void Main()
    {
        Console.WriteLine("Making Coffee:");
        Beverage coffee = new Coffee();
        coffee.PrepareBeverage();

        Console.WriteLine("\nMaking Tea:");
        Beverage tea = new Tea();
        tea.PrepareBeverage();
    }
}

Output:

Making Coffee:
Boiling water...
Brewing coffee...
Pouring into cup...
Adding sugar and milk...

Making Tea:
Boiling water...
Steeping the tea...
Pouring into cup...
Adding lemon...

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Benefits of the Template Method Pattern

✅ Code Reusability - Eliminates duplicate code by defining a common algorithm structure. ✅ Maintainability - Changes in the algorithm structure affect all subclasses consistently. ✅ Flexibility - Allows subclasses to customize steps without altering the overall workflow. ✅ Enforces Best Practices - Ensures a standard procedure is followed across different implementations.

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Use Cases for the Template Method Pattern

• Data Processing Pipelines – Standardizing steps while allowing variations in specific processing tasks.
• Workflow Automation – Implementing predefined workflows where some steps require customization.
• Report Generation – Defining report structure with different data formatting styles.
• UI Components – Standardizing rendering processes while allowing variations in styling.

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FAQs

1. How is the Template Method Pattern different from Strategy Pattern?

The Template Method Pattern defines a structure in a base class with customizable steps, whereas the Strategy Pattern allows completely interchangeable algorithms at runtime.

2. When should I use the Template Method Pattern?

Use it when you need to enforce a consistent algorithm structure while allowing subclasses to define specific behavior.

3. Is the Template Method Pattern related to inheritance?

Yes, it relies on inheritance to allow subclasses to override specific methods while keeping the overall algorithm intact.

4. Can I use dependency injection with the Template Method Pattern?

Yes, dependency injection can be used for greater flexibility, allowing behaviors to be injected instead of relying solely on inheritance.

5. Is the Template Method Pattern outdated?

No, it remains a powerful pattern for defining reusable workflows, especially in structured application designs.

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Conclusion

The Template Method Pattern is an essential design pattern that helps standardize algorithm structures while allowing flexibility in implementation. By using this pattern, developers can create well-structured, reusable, and maintainable code, enhancing application scalability.

Next Steps:

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