iteratating through objects?

Newfie

the exammple here:

http://beeblex.com/manual/language.oop5.iterations.html?s=man%3A+echo

shows the iteratation through one object. How can i store mulitple "people" objects and iterate through each name?

Newfie

for example in this code i have here:



<?php
include_once 'StudentClass.php';	// Our business logic
class MyIterator implements Iterator
{
   private $var = array();

   public function __construct($array)
   {
       if (is_array($array)) {
           $this->var = $array;
       }
   }

   public function rewind() {
       echo "rewinding\n";
       reset($this->var);
   }

   public function current() {
       $var = current($this->var);
       echo "current: $var\n";
       return $var;
   }

   public function key() {
       $var = key($this->var);
       echo "key: $var\n";
       return $var;
   }

   public function next() {
       $var = next($this->var);
       echo "next: $var\n";
       return $var;
   }

   public function valid() {
       $var = $this->current() !== false;
       echo "valid: {$var}\n";
       return $var;
   }
}

$student = &new StudentClass;
$student->setUserName("TestName");
$values = array($student);
$it = new MyIterator($values);

foreach ($it as $a => $b) {
   print "$a->getUserName() === $b\n";
}
?>

i have added the student to an array. How do i get their name inside the foreach loop?

and how do i append an array so i can add more students?

for ($i=0;$i<10;$i++)
{
$student = &new StudentClass;
$student->setUserName("TestName");

$values = array();
$values[] = $student->getUserName();
$it = new MyIterator($values);

}

foreach ($it as $a => $b) {
print "$a === $b\n";
}

rvdavid

The way I do my iterators, I work with the source of the collection and instantiate upon request. This way, I am only passing around the source and not an array of instantiated objects.

Your "current()" method would be doing the instantiation and returning the instantiated object as required.

So if you acquire the data for people from a mysql database, you'd pass around the result set. Current would read the result set and return an instance of a new people object.

Regards,

Newfie

any example of this?

rvdavid

Sure...

Check out php patterns: http://www.phppatterns.com/docs/design/the_iterator_pattern

Sorry for being lazy, it's in PHP4 and does not use SPL, but it gives you an idea of what the iterator pattern is all about.

Regards,

Newfie

hmm it still doesn't explain how i'd store the object "Person" i.e. with the variables name, age, gender inside a collection and loop over multiple ones and how to append it. I'm lost. In JSP it was far much easier.

rvdavid

I'm sorry, I've strayed from your question...

To answer your question so that it fits what you want it to do, then I guess you could just add another method to the Iterator class in the example.

class MyIterator implements Iterator
{

//... other methods from the example here

public function add(StudentClass $student) 
{
    $this->var[] = $student; // add another student to stack
}

}

Implementation

$students = array(); //.. your array of students
$iterator = new MyIterator($students);
$student = new StudentClass;
$student->setUserName('someuser');
$iterator->add($student);

Newfie

hi thanks it works perfectly apart from one thing. When i loop over it i have to add 2 elements before it iterates:


$students = array(); //.. your array of students
$iterator = new MyIterator($students);
$student = new StudentClass;
$student->setUserName('someuser');
$iterator->add($student);
$iterator->add($student);
$iterator->add($student);






for ($i=0; $elem = $iterator->next(); $i++) {
    echo $iterator->current()->getUserName();
}

works fine.

but if i change:


$iterator = new MyIterator($students);
$student = new StudentClass;
$student->setUserName('someuser');
$iterator->add($student);

the loop never runs because there's no "next".hmm..

rvdavid

Hi there,

I'm afraid I don't understand. What do you mean? all the the add method does is adds to the $var stack.


$students = array();
$iterator = new MyIterator($students);
$student = new StudentClass;
$student->setUserName('someuser');
$iterator->add($student);
$iterator->add($student);

print_r($iterator);

This worked for me.

Regards,

Newfie

hi i fixed it this is what i meant:


for ($i=0; $elem = $iterator->valid(); $i++) {

echo $iterator->current()->getUserName();
$iterator->next();
}

rvdavid

Ahh I see.

Instead of shoehorning the iterator inside a for loop, why don't you use the alternative looping functions like.

foreach()

foreach($iterator as $student) {
	echo $student->getUserName();
}

or while()

while($student = $iterator->current()) {
	echo $student->getUserName();
}

Regards,

Newfie

hi, thanks the foreach looks more efficient. I think i'll use that 🙂

rvdavid

no probs 🙂

good luck with it.