[RESOLVED] Looping through multi-dimensional class object of unknown size

[vertmonkee]

I am pulling in a stdClass Object from a web service and it can have an uknown number of dimensions to it.

It could look like this

[AphiaID] => 106680
[rank] => Subsection
[scientificname] => Heterotremata
[child] => stdClass Object (
                      [AphiaID] => 106695
                      [rank] => Superfamily
                      [scientificname] => Cancroidea
                      [child] => stdClass Object (
                                          [AphiaID] => 106749
                                          [rank] => Family
                                          [scientificname] => Cancridae
                                          [child] => stdClass Object (
                                                              [AphiaID] => 106876
                                                              [rank] => Genus
                                                              [scientificname] => Cancer
                                                              [child] =>
                                         )
                       )
)

Or it could be simpler like so

[AphiaID] => 106680
[rank] => Subsection
[scientificname] => Heterotremata
[child] => stdClass Object (
                     [AphiaID] => 106876
                     [rank] => Genus
                     [scientificname] => Cancer
                     [child] =>
)

Basically I won't know the size of it.

What I want to do is loop through and output the rank and scientific name until the child is not an stdClass object.

I'm completley stumped, can anyone help me out please.

[halojoy]

It sounds like a recursive function using foreach loop

it shouldnt be too difficult
but too difficult for me, right now ..... need to make some food 🙂

[johnpeace]

it shouldnt be too difficult

That's what everyone says about recursive functions...but it's never proven true for me.

[laserlight]

johnpeace wrote:

That's what everyone says about recursive functions...but it's never proven true for me.

I will concede that sometimes they can be difficult, but in this case it looks so easy that iteration will suffice without the need of an explicit stack. Basically, one can keep looping as long as the object is not empty. In the loop, output the rank and scientific name, then set the object reference to refer to the current object's child.

[vertmonkee]

Thanks for the inpsiration.

This is what I came up with

	function ranksArray($std_object, $passed_array = false) {

	// Create the rank array if one is not passed in
	if($passed_array == false) {
		$rank_array = array();
	} else {
		$rank_array = $passed_array;
	}

	// Add items to the array
	if(is_object($std_object)) {

		// Add the key and value
		$rank_array[$std_object->rank] = $std_object->scientificname;

		if(is_object($std_object->child)) {
			return $this->ranksArray($std_object->child, $rank_array);
		} else {
			return $rank_array;
		}

	}

	return $rank_array;

}

[laserlight]

vertmonkee wrote:

This is what I came up with

An iterative solution is simply simpler:

function ranksArray($std_object) {
    $rank_array = array();

// Add items to the array
while (is_object($std_object)) {
    // Add the key and value
    $rank_array[$std_object->rank] = $std_object->scientificname;

    // Traverse to the child of the current object
    $std_object = $std_object->child;
}

return $rank_array;
}

[johanafm]

In my experience, people either find iteration or recursion easier. Personally, if I did not stop to think, I would automatically deal with this through recursion. However, while recursion often produce simpler (once again, may be a matter of personal preference) it does not come without cost. There is overhead for function calls, such as pushing local variables on the stack along with a return pointer. Some things can't be handled in a generic fashion other than with recursion, as is the case with tail recursion if my memory serves me, but if they can it might actually be a good idea to choose iteration. Especially if there is deep nesting.

function visit($o) {
	if ($o === null)
		return;
	echo 'Object<br/>';
	# will output aphiaID as well, but that can easily be checked for. or ditch the loop and use implicit element referencing.
	foreach($o as $k => $v) {
		if (is_object($v)) {
			echo $k . ' => {<div style="margin-left: 26px;">';
			visit($v);
			echo '</div>}';
		}
		else
			echo $k . ': ' . $v . '<br/>';
	}
}

visit($c);

[laserlight]

johanafm wrote:

Some things can't be handled in a generic fashion other than with recursion, as is the case with tail recursion if my memory serves me, but if they can it might actually be a good idea to choose iteration.

You remembered the opposite 🙂
It is easy to convert tail recursion to iteration, and in fact vertmonkee's uses tail recursion. Nonetheless, it is always possible to convert recursion to iteration, by using an explicit stack if necessary.

All this might become easier if we recognise that we are dealing with a singly linked list.

[johanafm]

laserlight;10942909 wrote:

All this might become easier if we recognise that we are dealing with a singly linked list.

Which I usually fail to see initially, unless the class is called list and member child is called next :p