PHP: Object oriented example (Homework)

Well, there's a few things to thing about here, but you know that you need $age and $color properties, and ways to read those properties. Chances are, you don't want to be able to write them though.

So, I would probably have:

getAge(){ return $this->age; }
getColor(){ return $this->color; }

Now, you want to assign the color and age randomly, which means you need the rand function (there are other options there, but rand will do you well). Now, if I were to do this, I would put something like this in the constructor:

// assuming we're testing for male or female
// you really should look into why this works.
$this->gender = ( rand( 0, 1 ) )? self::MALE: self::FEMALE;
// notice the self::MALE and self::FEMALE? Those are class constants.
// http://php.net/manual/en/language.oop5.constants.php
// if you want to get this question *right* you'll need to look at those

Your machines are actually pretty simple. They only test whether each sheep is old enough to be shorn and then they increment a counter based on that.

// assuming they are looking for a count of female sheep
// and state variables 'male' and 'female' which are initialized at 0
function processSheep( $sheep )
{
    foreach( $sheep as $test )// stupid self-pluralizing nouns.
    {
        if( $sheep->getGender() == Sheep::MALE ) $this->males++;
        else $this->females++; // obviously, you're going to need to swap
                               // out one of these increments for an echo.
    }
}

function getNumberOfMales(){ return $this->males; }

With two machines, to calculate the number of males:

$mach1->getNumberOfMales() + $mach2->getNumberOfMales();

With an array of n machines, the number of males:

$males = 0;
foreach( $machs as $mach ){ $males += $mach->getNumberOfMales(); }

What types of things are there in your program? Sheep and machines.

Should sheep and machines be the same class? Well, do they share the same attributes? Do machines have age? No. Do machines have color? No. Then they're not the same class.

Make a sheep class, give it age and color properties. The class constructor should randomly assign the values of the age and color properties so they're set when each sheep object is created.

Make a machine class. It needs properties to hold how much black wool and how much white wool it has collected.

Create setters and getters for the properties in both classes.

Now write the program which creates the sheep and machine objects, and performs the required task.

Expanding on TomcatExodus:

<?php 

class Sheep{

    const COLOR_WHITE = 'white';
    const COLOR_BLACK = 'black';
    const AGE_YOUNG = 0;
    const AGE_OLD = 1;

    private $_color;
    private $_age;
    private $_sheered;

    public function makeRandom() {
        $this->_color = rand(0, 1)
            ? self::COLOR_WHITE
            : self::COLOR_BLACK;
        $this->_age = rand(0, 1);
    }

    public function __construct(){
        $this->makeRandom();
    }

    public function sheer() {
        if($this->_age == 0) {
            $this->_sheered['This sheep is not ready to be sheared.'] = $this->_sheered['This sheep is not ready to be sheared.'] + 1;
        } else {
            if($this->_color == 'black') {
                $this->_sheered['black'] = $this->_sheered['black'] + 1;
            } else {
                $this->_sheered['white'] = $this->_sheered['white'] + 1;
            }
        }
    }

    public function results() {
        return print_r($this->_sheered,true);
    }
}

$batch = 20;
$sheep = new Sheep();

while($batch > 0) {
    $sheep->makeRandom();
    $sheep->sheer();
    $batch--;
}
echo $sheep->results()."\n";

?>