Improving the Code One Line at a Time

In previous episodes, we showed some heuristics to find not so good code. Code Smells Part I Part II Part III Part IV Part V Part VI Part VII Part VIII Part IX Part X Part XI Part XII Part XIII Part XIV Part XV Part XVI Part XVII Part XVIII Part XIX Part XX Let’s fixed them! Refactoring 001 - Remove Setters Setters violate immutability and add accidental coupling TL;DR: Make your attributes private to favor mutability Problems Addressed Mutability setXXX() violates good naming policies since it does not exist on the MAPPER Accidental coupling Related Code Smells Code Smell 28 - Setters Code Smell 01 - Anemic Models Steps Locate the setters' usage If you are setting essential properties move them to the constructor and remove the method If you need to change an accidental property it is not a setter. Remove the setXXX prefix Sample Code Before public class Point { protected int x; protected int y; public Point() { this.x = 0; this.y = 0; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } } Point location = new Point(); //At this momment, it is not clear which points represent //It is coupled to constructor decision. //Might be null or some other convention location.setX(1); //Now we have point(1,0) location.setY(2); //Now we have point(1,2) public class Car { protected int speed; public Car() { } public void setSpeed(Speed desiredSpeed) { this.speed = desiredSpeed; } } Car tesla = new Car(); //We have no speed?? tesla.setSpeed(100 km/h); //Now our car runs fast After //1. We locate setters usage location.setX(1); location.setY(2); //2. If you are setting essential properties move //them to the constructor and remove the method public class Point { public Point(int x, int y) { this.x = x; this.y = y; //We remove the setters } Point location = new Point(1, 2); public class Car { protected int speed; public Car() { this.speed = 0 km/h; } public void speed(Speed desiredSpeed) { this.speed = desiredSpeed; } } //1. Locate the setters' usage //3. If you need to change an accidental property // it is not a setter. Remove the setXXX prefix Car tesla = new Car(); //Our car is stopped tesla.speed(100 km/h); //We tell the desired speed. We don't set anything //We don't care if the car stores its new speed. //if it manages through the engine //if the road is moving etc Type Semi-Automatic [x] We should detect setters (unless they use meta-programming) with our IDEs. We can also remove them and see which tests fail if we have good coverage Tags Mutability Related Refactorings Remove Getters Pass essential properties in the constructor Initialize essential properties in the constructor Credits Image by on Comfreak Pixabay Refactoring 002 - Extract Method Find some code snippets that can be grouped and called atomically. TL;DR: Group your cohesive sentences together Problems Addressed Readability Complexity Code Reuse Related Code Smells Code Smell 03 - Functions Are Too Long Code Smell 05 - Comment Abusers Code Smell 18 - Static Functions Code Smell 22 - Helpers Code Smell 74 - Empty Lines Code Smell 78 - Callback Hell Code Smell 102 - Arrow Code Steps Move the code fragment to a separate new method Replace the old code with a call to the recently created method. Sample Code Before object Ingenuity { fun moveFollowingPerseverance() { // take Off raiseTo(10 feet) // move forward to perseverance while (distanceToPerseverance() < 5 feet) { moveForward() } // land raiseTo(0 feet) } After object Ingenuity { //1. Move the code fragment to a separate new method private fun takeOff() { raiseTo(10 feet) } //1. Move the code fragment to a separate new method private fun moveForwardToPerseverance() { while (distanceToPerseverance() < 5 feet) { moveForward() } } //1. Move the code fragment to a separate new method private fun land() { raiseTo(0 feet) } fun moveFollowingPerseverance() { takeOff() //2. Replace the old code with a call to the recently created method. moveForwardToPerseverance() //2. Replace the old code with a call to the recently created method. land() //2. Replace the old code with a call to the recently created method. } } Type Automatic [x] Many IDEs support this safe refactoring Why code is better? Code is more compact and easier to read. Functions can be reused. Algorithms and functions are more declarative hiding implementative details on extracted code. Limitations Does not work well if you use . meta-programming anti-pattern Tags Complexity Readability Related Refactorings Move method to a new class Credits Image by on Hreisho Pixabay Refactoring 003 - Extract Constant You need to use some values explaining their meaning and origin TL;DR: Name all your magic numbers Problems Addressed Readability Complexity Code Reuse Related Code Smells Code Smell 02 - Constants and Magic Numbers Steps Move the constant code fragment to a constant declaration Replace the values with a reference to the constant. Sample Code Before double energy(double mass) { return mass * 300.000 ^ 2; } After //1. Move the constant code fragment to a constant declaration final double LIGHT_SPEED = 300.000; double energy(double mass) { //2. Replace the old code with a reference to the constant. return mass * LIGHT_SPEED ^ 2; } Type Automatic [x] Many IDEs support this safe refactoring Why code is better? Constant names add meaning to our code. Magic numbers are difficult to understand and change. Code must be as declarative as possible. Tags Readability Related Refactorings Refactoring 002 - Extract Method Credits Image by on Tumisu Pixabay Refactoring 004 - Remove Unhandled Exceptions Creating YAGNI exception classes pollutes our environment. Let's remove them. TL;DR: Remove unnecessary and not references empty exception classes. Problems Addressed Empty Classes Namespace Polluted Related Code Smells Code Smell 26 - Exceptions Polluting Steps Check there are no references to the empty exception class. Replace the throw sentence with a generic one. Sample Code Before class RangeNotSatisfiedException e puts e.message puts e.exception_type end After # 1. Check there are no references to the empty exception class. # 2. Replace the throw sentence with a generic one. begin raise StandardError.new "Range must be betweet 0 and 10" rescue StandardError => exception puts exception.message puts exception.exception_type end Type Automatic [x] If the Exception class has no references we can perform a Safe Remove and replace it with class. Exception Why the code is better? We remove an empty class nobody uses. We shrink the code Limitations If we need to declare an empty exception class as documentation for an API module, our clients might need to catch it. This is a and example. gold plating YAGNI Tags Clean up Related Refactorings Safe Remove Credits Image by on danielkirsch Pixabay Refactoring 005 - Replace Comment with Function Name Comments should add value. And function names too. TL;DR: Don't comment on what you are doing. Name what you are doing. Problems Addressed Bad Names Comments Related Code Smells Code Smell 05 - Comment Abusers Code Smell 75 - Comments Inside a Method Code Smell 06 - Too Clever Programmer Steps Name the function with the previous comment Remove the Comment Sample Code Before <? function repl($str) { // Replaces with spaces the braces $str = str_replace(array("\{","\}")," ",$str); return $str; } After <? // 1. Name the function with the previous comment // 2. Remove the Comment function replaceBracesWithSpaces($input) { return str_replace(array("\{","\}")," ", $input); } Type Semi-Automatic [x] Some IDEs have this refactoring although naming is not fully automatic. Why the code is better? Comments always lie. It is hard to maintain comments. On the contrary, Functions are alive and self-explanatory. Limitations As always, very important design decisions are valid comments. Tags Comments See also What is in a name? Credits Image by on Jannik Texler Pixabay This article is part of the Refactoring Series. More smells and more refactorings are on the way!