Design principles SOLID Design principles circle class Circle

Design principles SOLID Design principles

//circle class Circle { public $radius; public function __construct($radius) { $this->radius = $radius; } } //Square class Square { public $length; } public function __construct($length) { $this->length = $length; } //Area Calculator class Area. Calculator { protected $shapes; public function __construct($shapes = array()) { $this->shapes = $shapes; } public function sum() { // logic to sum the areas } public function output() { return implode('', array( "", "Sum of the areas of provided shapes: ", $this->sum(), "" )); } }

//instantiate $shapes = array( new Circle(2), new Square(5), new Square(6) ); $areas = new Area. Calculator($shapes); echo $areas->output();

SOLUTION $shapes new new ); = array( Circle(2), Square(5), Square(6) $areas = new Area. Calculator($shapes); $output = new Sum. Calculator. Outputter($areas); echo $output->JSON(); echo $output->HAML(); echo $output->HTML();

Employee Class public class Employee{ private String employee. Id; private String name; private string address; private Date date. Of. Joining; public boolean is. Promotion. Due. This. Year(){ //promotion logic implementation } public Double calc. Income. Tax. For. Current. Year(){ //income tax logic implementation } //Getters & Setters for all the private attributes }

Solution public class Fin. ITCalculations{ public Double calc. Income. Tax. For. Current. Year(Employee emp){ //income tax logic implementation using the employee information passed } } ******** public class HRPromotions{ public boolean is. Promotion. Due. This. Year(Employee emp){ //promotion logic implementation using the employee information passed } } ******* public class Employee{ private String employee. Id; private String name; private string address; private Date date. Of. Joining; //Getters & Setters for all the private attributes

Open-closed principle //sum method of area calculator class public function sum() { foreach($this->shapes as $shape) { if(is_a($shape, 'Square')) { $area[] = pow($shape->length, 2); } else if(is_a($shape, 'Circle')) { $area[] = pi() * pow($shape->radius, 2); } } return array_sum($area); }

Solution class Square { public $length; public function __construct($length) { $this->length = $length; } public function area() { return pow($this->length, 2); } } ********* public function sum() { foreach($this->shapes as $shape) { $area[] = $shape->area(); } return array_sum($area);

interface Shape. Interface { public function area(); } class Circle implements Shape. Interface { public $radius; public function __construct($radius) { $this->radius = $radius; } } public function area() { return pi() * pow($this->radius, 2); }

Solution public function sum() { foreach($this->shapes as $shape) { if(is_a($shape, 'Shape. Interface')) { $area[] = $shape->area(); continue; } } } throw new Area. Calculator. Invalid. Shape. Exception; return array_sum($area);

Liskov’s substitution principle Let p(X) be a property provable about objects X of type T. Then p(Y) should be true for object Y of type S. Where S is subtype of T.

Interface segregation principle interface Shape. Interface { public function area(); public function volume(); }

SOLUTION interface Shape. Interface { public function area(); } interface Solid. Shape. Interface { public function volume(); } class Cuboid implements Shape. Interface, Solid. Shape. Interface { public function area() { // calculate the surface area of the cuboid } } public function volume() { // calculate the volume of the cuboid }

Dependency inversion principle class Password. Reminder { private $db. Connection; } public function __construct(My. SQLConnection $db. Connection) { $this->db. Connection = $db. Connection; }

interface EBook { function read(); } class EBook. Reader { private $book; function __construct(EBook $book) { $this->book = $book; } function read() { return $this->book->read(); } } class PDFBook implements EBook{ function read() { return "reading a pdf book. "; }

Solution interface DBConnection. Interface { public function connect(); } class My. SQLConnection implements DBConnection. Interface { public function connect() { return "Database connection"; } } class Password. Reminder { private $db. Connection; } public function __construct(DBConnection. Interface $db. Connection) { $this->db. Connection = $db. Connection; }