PHP: Ensure that an array contains objects from only a certain class

Question

In some of my setters, I pass an array of objects. I would like to ensure that it only contains instances from a given class. Reading the doc, here is what I do :

class Foo
{
    public function __construct()
    {

    }
}

class ErrorFoo
{
    public function __construct()
    {

    }
}

$arrayObject = Array();

array_push($arrayObject, new Foo());
array_push($arrayObject, new Foo());
array_push($arrayObject, new ErrorFoo());

$error = false;
foreach ($arrayObject as $obj)
{
    if ( $obj instanceof Foo ) 
    {
        echo "ok" . '<br>';
    }
    else 
    {
        echo "error" . '<br>';
        $error = true;  
    }
}

Do you know a simpler way than iterate through the array like this?

As part of your setter function you can validate the passed object type? Throwing exceptions if the type doesnt match what you want. Doing this will ensure the object returned in any getters are of the type expected. — JParkinson1991
– JParkinson1991, Commented Sep 4, 2017 at 11:06
@Goon3r If I pass an array as parameter, then the passed object type is Array, no ? — snoob dogg
– snoob dogg, Commented Sep 4, 2017 at 11:09

axiac · Accepted Answer · 2017-09-04 11:18:24Z

Create a class that extends ArrayObject, redefine its offsetSet() method and do the check in it. Use this class instead of a plain array to store the objects of type Foo.

class ArrayOfFoo extends ArrayObject
{
    public function offsetSet($index, $newval)
    {
        // Verify the input 
        if (! $newval instanceof Foo) {
            // do something
            throw new InvalidArgumentException('Invalid type');
        }

        // Let the parent class do its job
        parent::offsetSet($index, $newval);
    }
}

This code throws an exception when the object of type ErrorFoo is added to the array:

$ArrayObject = new ArrayOfFoo();

$ArrayObject[] = new Foo();
$ArrayObject[] = new Foo();
// This throws an exception
$ArrayObject[] = new ErrorFoo();

An instance of the ArrayObject class can be used in the same way an array is used (setting, unsetting and fetching values from it). Its method getArrayCopy() can be used to get an array that can be passed as argument to functions that expect arrays (explode(), f.e.)

Lucas Bustamante · Accepted Answer · 2023-07-12 11:49:10Z

3

One alternative is using variadics to enforce types. It's an array inside the function, but not outside:

function doSomething(MyObject ...$array)
{
     // $array contains only MyObject instances in it
}

doSomething(new MyObject, new MyObject, new MyObject);

edited Jul 12, 2023 at 11:49

answered May 29, 2019 at 22:04

Lucas Bustamante

17.6k9 gold badges101 silver badges94 bronze badges

Comments

ansidev · Accepted Answer · 2018-11-23 10:46:05Z

0

You could use array_map or array_walk for this:

https://php.net/manual/en/function.array-map.php

Example of array_map:

function isInstanceOfFoo($n)
{
    if(!($n instanceof Foo)) {
      throw new Exception('Error');
    }
}

$ArrayObject = Array();

array_push($ArrayObject, new Foo());
array_push($ArrayObject, new Foo());
array_push($ArrayObject, new ErrorFoo());

array_map(isInstanceOfFoo, $ArrayObject);

https://php.net/manual/en/function.array-walk.php

Example of array_walk:

function isInstanceOfFoo($n, $k)
{
    if(!($n instanceof Foo)) {
      throw new Exception('Error');
    }
}
array_walk($ArrayObject, isInstanceOfFoo);

edited Nov 23, 2018 at 10:46

ansidev

3711 gold badge3 silver badges19 bronze badges

answered Sep 4, 2017 at 11:07

enno.void

6,6284 gold badges28 silver badges45 bronze badges

2 Comments

snoob dogg Over a year ago

the links are /de/ instead of /en/ can't edit that because It needs at least 6 characters

Nigel Ren Over a year ago

You could extend this to pass the class name - so becomes function isInstanceOf( $class, $n) and test becomes $n instanceOf $class. It's like using Javas generics.

Collectives™ on Stack Overflow

PHP: Ensure that an array contains objects from only a certain class

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related