We have covered several approaches that focus on method-level refactoring techniques. But what about scenarios when entire classes need intervention? In this and several following lessons, we will focus on just that.

This lesson will explain the sprout class technique, which is particularly useful when dealing with classes that have taken on too many responsibilities. This technique helps in breaking down complex classes into more manageable and focused components, improving both readability and maintainability.

In software development, it's common to encounter classes that have grown too large and complex over time. These overburdened classes often handle multiple responsibilities, making them difficult to understand and maintain. Signs of such classes include long methods, numerous dependencies, and a mix of unrelated functionalities. For instance, a class that manages both order processing and metrics collection is doing too much.

The sprout class technique is a powerful refactoring strategy that involves extracting cohesive responsibilities from an overburdened class into a new class. This approach aligns with the single responsibility principle, which states that a class should have only one reason to change. By creating a new class to handle specific tasks, we can simplify the original class and make the codebase more modular. This not only enhances readability but also makes the code easier to test and maintain.

Let's walk through the process of applying the sprout class technique using a practical example. Back to the order processor!

Here's a simplified version of the OrderProcessor class before refactoring:

C#
Copy to clipboard
1public class OrderProcessor
2{
3    private readonly IDatabase _database;
4
5    public OrderProcessor(IDatabase database)
6    {
7        _database = database;
8    }
9
10    public bool ProcessOrder(Order order)
11    {
12        // ... some order processing logic ...
13        
14        var todayOrders = _database.GetOrdersCreatedToday();
15        var totalRevenue = todayOrders.Sum(o => o.TotalAmount);
16        // ... other metrics related data ...
17
18        _database.SaveMetric("daily_orders", todayOrders.Count);
19        _database.SaveMetric("daily_revenue", totalRevenue);
20        // ... other metrics storage processes ...
21    }
22}

We can start by identifying the distinct responsibilities within the class. In this version, order processing and metrics collection are two separate concerns. We can extract the metrics collection logic into a new class called OrderMetricsCollector.

After applying the sprout class technique, the OrderProcessor class becomes more focused:

C#
Copy to clipboard
1public class OrderProcessor
2{
3    private readonly IDatabase _database;
4    private readonly OrderMetricsCollector _metricsCollector;
5
6    public OrderProcessor(IDatabase database)
7    {
8        _database = database;
9        _metricsCollector = new OrderMetricsCollector(database);
10    }
11
12    public bool ProcessOrder(Order order)
13    {
14        // ... some order processing logic ...
15        _metricsCollector.CollectMetricsForOrder(order, processingTime);
16    }
17}

The OrderMetricsCollector class now handles the metrics collection.

The sprout class technique offers several benefits, including improved modularity, enhanced readability, and easier testing. By isolating specific responsibilities into separate classes, we can focus on each aspect independently, leading to cleaner and more maintainable code. However, it's vital to avoid creating classes that are too granular or lack cohesion. Each new class should have a clear and focused purpose, ensuring that the refactoring effort truly enhances the codebase.

Refactoring with the sprout class technique impacts testing strategies. After extracting responsibilities into a new class, it's crucial to ensure that both the original and new classes are thoroughly tested. This involves writing unit tests for the new class to verify its functionality and updating existing tests for the original class to reflect the changes. By maintaining comprehensive test coverage, we can confidently refactor and enhance our code without introducing new bugs.

In this lesson, we explored the sprout class technique as a solution for refactoring overburdened classes. By identifying distinct responsibilities and extracting them into new classes, we can improve code modularity, readability, and maintainability. As we move on to the practice exercises, we'll have the opportunity to apply these concepts and reinforce our understanding of the sprout class technique. Thank you for joining us on this journey to mastering refactoring techniques!