I'm looking to create an array or list with elements of a certain type (eg objects the implement a certain interface). I know I can create an object that does the same thing implementing Traversable and Iterator, or override ArrayObject. But maybe there's another way I have missed.
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Please elaborate. Is your background Java?KahWee Teng– KahWee Teng2009-07-20 11:48:58 +00:00Commented Jul 20, 2009 at 11:48
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My bad, those objects did exist in PHP.KahWee Teng– KahWee Teng2009-07-20 11:49:45 +00:00Commented Jul 20, 2009 at 11:49
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I don't believe there are better ways than the ones you already mentioned.Ionuț G. Stan– Ionuț G. Stan2009-07-20 12:00:53 +00:00Commented Jul 20, 2009 at 12:00
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5 Answers
Do you mean something like:
$array=Array();
foreach ($itemsToAdd as $item) {
if ($item instanceof NameOfwantedInterface) {
Array_push($array,$item);
}
}
If you don't, them I'm sorry - it's just that your question isn't too clear.
2 Comments
koen
Yes that's the idea I'm looking for the enforce in a contract.
helloandre
PHP doesn't specifically assign types to arrays. This much be checked manually with a fuction like this.
I would write a custom class that extended ArrayObject and threw an exception if you tried to assign a variable that wasn't the correct type, there's really no better way to do it that I can think of.
Comments
PHP as a lanugage is very flexible in terms of type handling and type conversion. You will probably have to put a manual check in if you want any kind of strong type checking, a simple if statement will do.
The array object is designed to be especially flexible (lazy key assignment, automatic increment, string or integer keys, etc.) so you should probably use a custom object of your own.
Comments
You could use type hinting:
<?php
interface Shape
{
function draw();
}
class MyArray
{
private $array = array();
function addValue(Shape $shape) //The hinting happens here
{
$array[] = $shape;
}
}
?>
This example is not perfect, but you'll get the idea.
Comments
Basically, you are going to want to do a function that checks if the variable you are inserting into the array is an object.
function add($var)
{
if(is_object($var))
{
$this->array[] = $var;
}
}
If you want to make sure it has a specific class name, you would do something like this (for PHP5):
function add(className $var)
{
$this->array[] = $var;
}
or this for previous PHP versions:
function add($var)
{
if($var instanceOf className)
{
$this->array[] = $var
}
}
You might want to look into array_filter() to do this without building an object.
Looking at that page, I've found that you can use array_filter with common functions like is_object. So doing something like this:
$this->array = array_filter($this->array ,'is_object');
Would filter the array to contain only objects.
