6CC001 Workshop - week 02

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We are looking here at the examples already covered in class.

First, let's create our superclass:

• The common properties applies to all product types
• The constructor initializes all common properties.
• The getProducer assessor method allows access to the class's properties
• The getProductDetails public method returns a brief summary of the product (title and producer name)

// ShopProduct.php
class ShopProduct
{
  public $title;
  public $producerMainName;
  public $producerFirstName;
  public $price;
 
  function __construct($title, $firstName, $mainName, $price)
  {
    $this->title = $title;
    $this->producerFirstName = $firstName;
    $this->producerMainName = $mainName;
    $this->price = $price;
  }

  public function getProducer()
  {
    return "$this->producerFirstName 
            $this->producerMainName";
  }

  public function getProductDetails()
  {
    $s = "$this->title ($this->producerFirstName $this->producerMainName)";
    return $s;
  }
}

Let’s now create a couple of classes that extend our superclass…

First, a CDProduct class:

• It adds the “play length” property.
• It then overrides the constructor. It first calls the parent constructor to initialize the common properties, and then initializes the “play length” property.
• It adds a new assessor method, for the new “Play length” property.
• It also overrides the getProductDetails method, to add the new “play length” property to the product description.

// CdProduct.php

require_once("ShopProduct.php");

class CdProduct extends ShopProduct
{
  public $playLength;
  
  // Let's override the constructor
  function __construct($title, $firstName, $mainName, $price, $playLength)
  {
    parent::__construct($title, $firstName, $mainName, $price);
    $this->playLength = $playLength;
  }

 function getPlayLength()
  {
    return $this->playLength;
  }
  
  // Let's override getProductDetails
  function getProductDetails()
  {
    $s = parent::getProductDetails();
    $s.= " - playing time : $this->playLength";
    return $s;
  }
}

Likewise let's create a BookProduct class:

• It adds the “number of pages” property.
• It then overrides the constructor. It first calls the parent constructor to initialize the common properties, and then initializes the “number of pages” property.
• It adds a new assessor method, for the new “Number of pages” property.
• It also overrides the getProductDetails method, to add the new “number of pages” property to the product description.

// BookProduct.php

require_once("ShopProduct.php");

class BookProduct extends ShopProduct
{
  public $numPages;
  
  // Let's override the constructor
  function __construct($title, $firstName, $mainName, $price, $numPages)
  {
    parent::__construct($title, $firstName, $mainName, $price);
    $this->numPages = $numPages;
  } 

 function getNumberOfPages()
  {
    return $this->numPages;
  }  
  
  // Let's override getProductDetails
  function getProductDetails()
  {
    $s = parent::getProductDetails();
    $s.= " - number of pages : $this->numPages";
    return $s;
  }  
}

All done! Now let's test:

// test.php

require_once("CdProduct.php");
require_once("BookProduct.php");

$CD1 = new CdProduct("Back to black", "Amy", "Winehouse", 7.99, 63);
$CD2 = new CdProduct("Back to bedlam", "James", "Blunt", 7.99, 51);

$Book1 = new BookProduct("1984", "George", "Orwell", 8.99, 352);
$Book2 = new BookProduct("Never Let", "Kazuo", "Ishiguro", 7.99, 276);

echo $CD1->getProductDetails()."<br>";
echo $CD2->getProductDetails()."<br>";
echo $Book1->getProductDetails()."<br>";
echo $Book2->getProductDetails()."<br>";

Try it

Try creating and using new properties and methods in the classes above.