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POHow can I implement abstraction in this scenario?
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copied!<p>I have a parent class <code>Product</code> and two child classes: <code>Toothbrush</code> and <code>Chainsaw</code>. They are set-up as shown below. </p> <p>Here's the parent class:</p> <pre><code>class Product { protected $productid; protected $type; public function __construct( $productid ) { $this->productid = $productid; // Performs a lookup in the database and then populates the $type property } } </code></pre> <p>.. and here are the children:</p> <pre><code>class Toothbrush extends Product { public function getPrice() { return 5; // returning an integer for simplicity; there's a calculation going on here } } class Chainsaw extends Product { public function getPrice() { return 1000; // in USD } } </code></pre> <p>I want to iterate through a list of <code>$productid</code>'s and get the corresponding price of the items regardless of whether they are <code>chainsaw</code>'s or <code>toothbrush</code>es.</p> <h2>The problem (or is it?)</h2> <p>Now I've heard over and over again that <strong>a parent class should NOT rely on the child class</strong> to implement functionality (yes I read <a href="https://stackoverflow.com/questions/12934744/calling-a-child-method-from-the-parent-class-in-php">this question</a>, along with many others).</p> <p>Which is why I'm led to think that the solution I'm currently using (below) isn't optimal:</p> <pre><code>class Product { ... public function getPrice() { switch($this->type) { case 'toothbrush': $theproduct=new Toothbrush($this->productid); return $theproduct->getPrice(); break; case 'chainsaw': $theproduct=new Chainsaw($this->productid); return $theproduct->getPrice(); break; } } } </code></pre> <p>I can obviously sense that something is remiss here (I shudder to think of what would happen when I get 30 different product types). I've read about abstraction, interfaces, and inheritance and can't figure out which one would work in this scenario.</p> <p>Thank you!</p> <h2>EDIT</h2> <p>Seeing alot of answers, but none that've nailed it just yet. Here is the main point: <strong>How do I call a child method if have only a productid?</strong> (In the above scenario, the <code>Product</code> class retrieves the type from the database in the constructor and populates the <code>$type</code> property accordingly.</p>

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