Welcome to your next step in mastering Clean Code! 🚀 Previously, we emphasized the significance of naming conventions in clean coding. Now, we delve into the realm of functions and methods, which serve as the backbone of application logic and are crucial for code organization and execution. Structuring these functions effectively is vital for enhancing the clarity and maintainability of a codebase. In this lesson, we'll explore best practices and techniques to ensure our code remains clean, efficient, and readable.
Let's outline the key principles for writing clean functions:
- Keep functions small. Small functions are easier to read, comprehend, and maintain.
- Focus on a single task. A function dedicated to one task is more reliable and simpler to debug.
- Limit arguments to three or fewer. Excessive arguments complicate the function signature and make it difficult to understand and use.
- Avoid boolean flags. Boolean flags can obscure the code's purpose; consider separate methods for different behaviors.
- Eliminate side effects. Functions should avoid altering external states or depending on external changes to ensure predictability.
- Implement the DRY principle. Employ helper functions to reuse code, minimizing redundancy and enhancing maintainability.
Now, let's take a closer look at each of these rules.
Functions should remain small, and if they become too large, consider splitting them into multiple, focused functions. While there's no fixed rule on what counts as large, a common guideline is around 15 to 25 lines of code, often defined by team conventions.
Below, you can see the processOrder function which is manageable but has the potential to become unwieldy over time:
C++1void processOrder(Order& order, Inventory& inventory, Logger& logger) { 2 // Step 1: Validate the order 3 if (!order.isValid()) { 4 logger.log("Invalid Order"); 5 return; 6 } 7 8 // Step 2: Process payment 9 if (!order.processPayment()) { 10 logger.log("Payment failed"); 11 return; 12 } 13 14 // Step 3: Update inventory 15 inventory.update(order.getItems()); 16 17 // Step 4: Notify customer 18 order.notifyCustomer(); 19 20 // Step 5: Log order processing 21 logger.log("Order processed successfully"); 22}
Given that this process involves multiple steps, it can be improved by extracting each step into a dedicated private function, as shown below:
C++1void processOrder(Order& order, Inventory& inventory, Logger& logger) { 2 if (!validateOrder(order, logger)) return; 3 if (!processPayment(order, logger)) return; 4 updateInventory(order, inventory); 5 notifyCustomer(order); 6 logOrderProcessing(logger); 7} 8 9bool validateOrder(Order& order, Logger& logger) { 10 if (!order.isValid()) { 11 logger.log("Invalid Order"); 12 return false; 13 } 14 return true; 15} 16 17bool processPayment(Order& order, Logger& logger) { 18 if (!order.processPayment()) { 19 logger.log("Payment failed"); 20 return false; 21 } 22 return true; 23} 24 25void updateInventory(Order& order, Inventory& inventory) { 26 inventory.update(order.getItems()); 27} 28 29void notifyCustomer(Order& order) { 30 order.notifyCustomer(); 31} 32 33void logOrderProcessing(Logger& logger) { 34 logger.log("Order processed successfully"); 35}
A function should embody the principle of doing one thing only. If a function handles multiple responsibilities, it may include several logical sections. Below you can see the saveAndNotifyUser function, which is both too lengthy and does multiple different things at once:
C++1void saveAndNotifyUser(User& user, DataSource& dataSource) { 2 // Save user to the database 3 const char* sql = "INSERT INTO users (name, email) VALUES (?, ?)"; 4 5 try { 6 Connection connection = dataSource.getConnection(); 7 PreparedStatement statement = connection.prepareStatement(sql); 8 // Set user details in the prepared statement 9 statement.setString(1, user.getName().c_str()); 10 statement.setString(2, user.getEmail().c_str()); 11 12 // Execute the update query to save user 13 statement.executeUpdate(); 14 } catch (SQLException &e) { 15 std::cerr << "SQL exception: " << e.what() << std::endl; // Handle SQL exception 16 } 17 18 // Send a welcome email to the user 19 webClientPost(user); 20}
To enhance this code, you can create two dedicated functions for saving the user and sending the welcome email. This results in dedicated responsibilities for each function and clearer coordination:
C++1void saveAndNotifyUser(User& user, DataSource& dataSource) { 2 saveUser(user, dataSource); 3 notifyUser(user); 4} 5 6void saveUser(User& user, DataSource& dataSource) { 7 const char* sql = "INSERT INTO users (name, email) VALUES (?, ?)"; 8 9 try { 10 Connection connection = dataSource.getConnection(); 11 PreparedStatement statement = connection.prepareStatement(sql); 12 statement.setString(1, user.getName().c_str()); 13 statement.setString(2, user.getEmail().c_str()); 14 statement.executeUpdate(); 15 } catch (SQLException &e) { 16 std::cerr << "SQL exception: " << e.what() << std::endl; // Handle SQL exception 17 } 18} 19 20void notifyUser(User& user) { 21 // Example logic to send email notification 22 std::cout << "Sending welcome email to " << user.getName() << "..." << std::endl; 23 // Email sending logic here 24}
Try to keep the number of function arguments to a maximum of three, as having too many can make functions less understandable and harder to use effectively. 🤔
Consider the saveAddress function below with five arguments, which makes the function less clean:
C++1void saveAddress(std::string street, std::string city, std::string state, std::string zipCode, std::string country) { 2 // Logic to save address 3}
A cleaner version encapsulates the details into an Address object, reducing the number of arguments and making the function signature clearer:
C++1void saveAddress(const Address& address) { 2 // Logic to save address 3}
Boolean flags in functions can create confusion, as they often suggest multiple pathways or behaviors within a single function. Instead, use separate methods for distinct behaviors. 🚫
The setFlag function below uses a boolean flag to indicate user status, leading to potential complexity:
C++1void setFlag(User& user, bool isAdmin) { 2 // Logic based on flag 3}
A cleaner approach is to have distinct methods representing the different behaviors:
C++1void grantAdminPrivileges(User& user) { 2 // Logic for admin rights 3} 4 5void revokeAdminPrivileges(User& user) { 6 // Logic to remove admin rights 7}
A side effect occurs when a function modifies some state outside its scope or relies on something external. This can lead to unpredictable behavior and reduce code reliability.
Below, the addToTotal function demonstrates a side effect by modifying an external state:
C++1// Not Clean - Side Effect 2int addToTotal(int value) { 3 total += value; // modifies external state 4 return total; 5}
A cleaner version, calculateTotal, performs the operation without altering any external state:
C++1// Clean - No Side Effect 🌟 2int calculateTotal(int initial, int value) { 3 return initial + value; 4}
Avoid code repetition by introducing helper functions to reduce redundancy and improve maintainability.
The printUserInfo and printManagerInfo functions below repeat similar logic, violating the DRY principle:
C++1void printUserInfo(const User& user) { 2 std::cout << "Name: " << user.name << std::endl; 3 std::cout << "Email: " << user.email << std::endl; 4} 5 6void printManagerInfo(const Manager& manager) { 7 std::cout << "Name: " << manager.name << std::endl; 8 std::cout << "Email: " << manager.email << std::endl; 9}
To adhere to DRY principles, use a generalized printInfo function that operates on a parent Person type:
C++1void printInfo(const Person& person) { 2 std::cout << "Name: " << person.name << std::endl; 3 std::cout << "Email: " << person.email << std::endl; 4}
In this lesson, we learned that clean functions are key to maintaining readable and maintainable code. By keeping functions small, adhering to the Single Responsibility Principle, limiting arguments, avoiding side effects, and embracing the DRY principle, you set a strong foundation for clean coding. Next, we'll practice these principles to further sharpen your coding skills! 🎓