Does your code spark joy? Refactoring techniques to make your life easier.

A presentation based on Martin Fowler's book:
Refactoring - Improving the design of existing code.

Transcript

1. 1 @jucycabrera Does your code spark joy? Refactoring techniques to make your life easier
2. 2 Juciellen Cabrera @jucycabrera Mother of a really smart boy PHP and Elephpants PHPWomen Living in Ireland Food lover Meme specialist Software Engineer at Smartbox Group
3. 3 @jucycabrera Why talk about Refactoring? And then ...
4. 4 @jucycabrera A change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior. Refactoring (noun) It’s also a common error to see refactoring as something to fix past mistakes or clean up ugly code.
5. 5 @jucycabrera The idea that building an application that will not undergo any changes are untrue most of the time. As people change code to achieve short-term goals, often without a full comprehension of the architecture, the code loses its structure. Loss of structure has a cumulative effect. You will find yourself refactoring ugly code, but good code also needs refactoring.
6. 6 @jucycabrera Self-testing code not only enables refactoring - it also makes it much safer to add new features, since any bugs introduced with the new feature can be quickly found and fixed. First things first...
7. 7 @jucycabrera Bad Smells Smudge, originally known as Cascão, is one of the main characters of Monica's Gang. He never takes a bath, he hates water and never, ever touches it.
8. 8 @jucycabrera Mysterious Name When you can’t think of a good name for something, it’s often a sign of a deeper issue.
9. 9 @jucycabrera Duplicated Code Means that every time you read these copies, you need to read them carefully to see if there’s any difference.
10. 10 @jucycabrera Long Function The longer the function, the more difficult is to understand. Large Class A class with too much code is a bad opportunity for duplicated code and chaos.
11. 11 @jucycabrera Shotgun Surgery When every time you make a change, you have to make a lot of little edits to a lot of different classes.
12. 12 @jucycabrera Long Parameter List Long parameter lists are often confusing. Primitive Obsession Primitive types, such as integers, floating pointing numbers and strings, don’t represent a type of data we are dealing with.
13. 13 @jucycabrera Speculative Generality Things created before they are needed. • Abstract class that isn’t doing much • Unnecessary delegation • Functions with unused parameters
14. 14 @jucycabrera Repeated Switches It also applies to if statement. When the same conditional switching logic appears in different places and you add a clause, it is necessary to find all switches and update them.
15. 15 @jucycabrera Message Chain Long line of getThis().
16. 16 @jucycabrera Comments When you feel the need to write a comment, first try to refactor the code so that any comment becomes unnecessary. Polemic topic!
17. 17 @jucycabrera List of Refactorings
18. 18 @jucycabrera Extract Function If you have to spend effort looking at a block of code trying to figure out what it’s doing then you should extract it into a function. Inline Function Inverse of Extract Function, where a function has a body as clear as the name.
19. 19 @jucycabrera Extract Class When you see a class that is too big to easily understand, you need to consider where it can be split. Inline Class When a class is no longer pulling its weight and shouldn’t be around anymore.
20. 20 @jucycabrera Hide Delegate Encapsulation means that modules need to know less about other parts of the system. Remove Middle Man Opposite of Hide Delegate. Law of Demeter.
21. 21 @jucycabrera Extract Variable Add a name to an expression that is complex and hard to read. Inline Variable When the name doesn’t really communicate more than the expression itself. Named properties PHP 8
22. 22 @jucycabrera Change Function Declaration | Rename Method A good name allows you to understand what the function does when you see it called. Rename Variable Naming things well is at the heart of a clear programming. Rename Fields Fields names are important especially when they are widely used across an application.
23. 23 @jucycabrera Encapsulate Collection Access to a collection variable may be encapsulated.
24. 24 @jucycabrera Introduce Parameters Object Groups of data that are often together could be replaced by a data structure. Replace Primitive with Object e.g. Phone number, money Preserve Whole Object Values from the same object passed as an argument can be replaced by passing the whole object.
25. 25 @jucycabrera Substitute Algorithm Replace the complicated logic with a simpler one by decomposing the method, or creating a new algorithm or even using a native function.
26. 26 @jucycabrera Move Function | Move Field A nested function to a top level, or between classes. Slide Statements Code is easier to understand when things related to each other appear together.
27. 27 @jucycabrera Split Loop You ensure you only need to understand one thing a time. Separate refactoring from optimization. $averageAge = 0; $totalSalary = 0; foreach ($people as $person) { $averageAge += $person->page; $totalSalary += $person->salary; } $averageAge = $averageAge / count($people); $averageAge = 0; $totalSalary = 0; foreach ($people as $person) { $averageAge += $person->page; } foreach ($people as $person) { $totalSalary += $person->salary; } $averageAge = $averageAge / count($people);
28. 28 @jucycabrera Remove Dead Code Commenting out dead code is a common habit. Don’t be afraid to delete dead code. We have version control. Joelma: One of Brazil’s Queens
29. 29 @jucycabrera Decomposite Conditional Apply “Extract Function” on the condition and each leg of the conditional. if ($date->before(SUMMER_START) || $date->after(SUMMER_END)) { $charge = $quantity * $winterRate + $winterServiceCharge; } else { $charge = $quantity * $summerRate; } if (isSummer($date)) { $charge = summerCharge($quantity); } else { $charge = winterCharge($quantity); }
30. 30 @jucycabrera Replace Nested Conditional with Guard Clauses By reversing the conditions for example. function getPayAmount() { if ($this->isDead) { $result = $this->deadAmount(); } else { if ($this->isSeparated) { $result = $this->separatedAmount(); } else { if ($this->isRetired) { $result = $this->retiredAmount(); } else { $result = $this->normalPayAmount(); } } } return $result; } function getPayAmount() { if ($this->isDead) { return $this->deadAmount(); } if ($this->isSeparated) { return $this->separatedAmount(); } if ($this->isRetired) { return $this->retiredAmount(); } return $this->normalPayAmount(); }
31. 31 @jucycabrera Replace Conditional with Polymorphism Create subclasses matching the branches of the conditional. abstract class Bird { // ... abstract function getSpeed(); // ... } class European extends Bird { public function getSpeed() { return $this->getBaseSpeed(); } } class African extends Bird { public function getSpeed() { return $this->getBaseSpeed() - $this->getLoadFactor() * $this->numberOfCoconuts; } } class NorwegianBlue extends Bird { public function getSpeed() { return ($this->isNailed) ? 0 : $this->getBaseSpeed($this->voltage); } } // Somewhere in Client code. $speed = $bird->getSpeed(); class Bird { // ... public function getSpeed() { switch ($this->type) { case EUROPEAN: return $this->getBaseSpeed(); case AFRICAN: return $this->getBaseSpeed() - $this->getLoadFactor() * $this->numberOfCoconuts; case NORWEGIAN_BLUE: return ($this->isNailed) ? 0 : $this->getBaseSpeed($this->voltage); } throw new Exception("Should be unreachable"); } // ... }
32. 32 @jucycabrera Introduce Special Case | Null Object A class that provides special behavior for particular cases. if ($customer === null) { $plan = BillingPlan::basic(); } else { $plan = $customer->getPlan(); } class NullCustomer extends Customer { public function isNull() { return true; } public function getPlan() { return new NullPlan(); } // Some other NULL functionality. } // Replace null values with Null-object. $customer = ($order->customer !== null) ? $order->customer : new NullCustomer; // Use Null-object as if it's normal subclass. $plan = $customer->getPlan();
33. 33 @jucycabrera Separate Query from Modifier A function that returns a value should not have observable side effects. The famous case of findAndDoSomethingElse.
34. 34 @jucycabrera Parameterize Function Functions that have similar logic with different values can be removed by using a single function with parameters.
35. 35 @jucycabrera Remove Flag Argument Flag argument is used to indicate which logic the function should execute. It’s clear to provide an explicit function for each task.
36. 36 @jucycabrera Replace Constructor with Factory Function By creating a single point where the class is instantiated you avoid tight coupling. class Employee { // ... public function __construct($type) { $this->type = $type; } // ... } class Employee { // ... static public function create($type) { $employee = new Employee($type); // do some heavy lifting. return $employee; } // ... }
37. 37 @jucycabrera Extract Super class Pull Up Method Pull Up Field Push Down Method Push Down Field Dealing with Inheritance
38. 38 @jucycabrera The key to effective refactoring is recognizing that you go faster when you take tiny steps Martin Fowler
39. 39 @jucycabrera Tips Keep an eye on updates PHP8 is live! Tests first! Create them if you don’t have any Tiny steps Don’t waste an opportunity to improve code Code review is a chance to discuss changes
40. 40 @jucycabrera Find more by Martin Fowler, with Kent Beck 2018 - 2nd edition https://martinfowler.com/books/refactoring.html Refactoring Improving the Design of Existing Code https://refactoring.guru
41. 41 Thank you Obrigada @jucycabrera