Hello, explorer! Today is about refactoring. Think of it as organizing your favorite tool chest. We're going to learn about Extract Method, Rename Method, and Substitute Algorithm refactorings in C++. Refactoring helps us tidy up our code, making it cleaner and more maintainable, all while preserving its functionality.
Consider having a complicated blueprint. Refactoring changes it into a clearer drawing. Our code is rearranged to enhance readability and efficiency without altering its behavior. Let's examine a short code snippet before and after refactoring:
C++1// Before refactoring 2double calculate(double total, int quantity) { 3 double price = total / quantity; 4 double tax = price * 0.2; 5 double totalPrice = price + tax; 6 return totalPrice; 7}
C++1// After refactoring 2double calculatePrice(double total, int quantity) { 3 return total / quantity; 4} 5 6double calculateTax(double price) { 7 return price * 0.2; 8} 9 10double calculateTotalPrice(double total, int quantity) { 11 double price = calculatePrice(total, quantity); 12 double tax = calculateTax(price); 13 return price + tax; 14}
Both code versions perform the same function, but the refactored version is simpler and easier to comprehend!
Imagine a large set of instructions for setting up a desktop. The Extract Method technique is like having separate instructions for the monitor, CPU, keyboard, etc., instead of one large set of instructions. Observe this code:
C++1// Before refactoring 2std::string greetUser(std::string username) { 3 // Prepare the username 4 std::transform(username.begin(), username.end(), username.begin(), ::tolower); 5 username.erase(username.find_last_not_of(" \n\r\t")+1); // Find the last non-whitespace character and erase everything after it 6 std::string message = "Hello, " + username + "!"; // Prepare the message 7 return message; // Return the prepared message 8}
C++1// After refactoring 2std::string cleanUsername(std::string username) { 3 // Returns a cleaned version of the username 4 std::transform(username.begin(), username.end(), username.begin(), ::tolower); 5 username.erase(username.find_last_not_of(" \n\r\t")+1); // Find the last non-whitespace character and erase everything after it 6 return username; 7} 8 9std::string greetUser(std::string username) { 10 username = cleanUsername(username); // Clean the username 11 std::string message = "Hello, " + username + "!"; // Prepare and return the message 12 return message; 13}
Here, we moved the username preparation from greetUser into its dedicated function cleanUsername. Neat and organized!
Clear method names make code comprehension easier, just as clear street names simplify city navigation. Let's look at renaming a method:
C++1// Before refactoring 2double fx(double x) { 3 return 3.14 * x * x; // Calculates a value that is pi times the square of x 4}
C++1// After refactoring 2double calculateCircleArea(double radius) { 3 return 3.14 * radius * radius; // Calculates the area of a circle with a given radius 4}
Renaming the function fx to calculateCircleArea makes understanding its purpose much easier.
Substitute Algorithm involves replacing a section of code (an algorithm) with a more efficient one, similar to finding a faster route to a destination. Here's an illustration:
C++1// Before refactoring 2int findSmallest(const std::vector<int>& numbers) { 3 int smallest = numbers[0]; 4 for (int num : numbers) { 5 if (num < smallest) { 6 smallest = num; 7 } 8 } 9 return smallest; 10}
C++1// After refactoring 2int findSmallest(const std::vector<int>& numbers) { 3 return *std::min_element(numbers.begin(), numbers.end()); // Returns the smallest number from 'numbers' 4}
The std::min_element function in C++ accomplishes the same task as our previous implementation but in a more concise and efficient manner.
Great job! We've learned how to use Extract Method, Rename Method, and Substitute Algorithm to keep our C++ code clean and efficient. Now, it's time for some hands-on practice with real-world examples. Remember, practice is key to mastering a skill. Let's get refactoring!