Setting Up Multiple Classes to Represent Real-World Objects

PHP: If I have a customer class, and the customer can have a car and an invoice, and I want to have separate car and invoice classes, what is the most efficient way of setting them up?

So, I have three different clas开发者_如何学运维ses:

customer.class.php

customer_car.class.php

customer_invoice.class.php

What's the best way to set up the relationship/initialization between the three classes? A customer can have a car or an invoice. I want to keep the code separated so that its easy to maintain.

$customer = new customer();
$car = $customer->newCar();
$invoice = $customer->newInvoice();

?

Here is just an idea as it may be structure differently to reflect your business logics...

Have 3 seperate classes customer, car and invoice.

Customers can can zero to many cars to them.

Customer can have zero to many invoices to them.

An invoice may belong to 1 and only 1 customer and able to have 1 to many cars.

Illustration of a customer class:

class Customer 
{
    var $cars = array();
    var $invoices = array();

    function Customer() { }

    function OwnCar($car)
    {
        $cars[] = $car;
    }

    function OwnInvoice($invoice)
    {
        $invoices[] = $invoice;
    }
}

Illustration of usage:

$customerA = new Customer();
$carA = new Car();
$invoiceA = new Invoice($customerA, array($carA));

$customerA->OwnCar($carA);
$customerA->OwnInvoice($invoiceA);

Note: Illustration code is in PHP4, where you may feel free (also recommanded) to develop with PHP5 syntax.

why not

$customer = new customer();
$car = new car();
$invoice = new invoice();

$car->SetOwner($customer);
$invoice->SetCustomer($customer);

Think about adding a new item, such as Payment. How much additional work is necessary with your approach vs. mine. This sounds like a homework problem, so I won't spell it out.

None of the three classes are related at all. so the simple answer is in the question. Create two variables within the customer class that can hold a car class and an invoice class.

Remember within OOP use the ISA HASA relationships in other words the customer is not a car nor an invoice but the customer has a car and an invoice so in both cases it matches HASA.

The customer ISA person though so you could extend the customer class from a person class.

class customer extends person {
    private $invoice; // variable to hold invoice
    private $car;     // variable to hold car

   ...
}

DC