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ArrayAccess interface, Traversable interface and foreach [message #185987]

Fri, 23 May 2014 14:22

kurtk(at)pobox(dot)com
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The documentation for ArrayAccess (at http://www.php.net/manual/en/class.arrayaccess.php) doesn't show it implementing Traversable. Nevertheless, you can still use any class you write that implements ArrayAccess in a foreach loop.

This seems like an oversight in the documentation--unless I am missing something?

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Re: ArrayAccess interface, Traversable interface and foreach [message #185988 is a reply to message #185987]

Fri, 23 May 2014 16:35

Jerry Stuckle
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On 5/23/2014 2:22 PM, kurtk(at)pobox(dot)com wrote:
> The documentation for ArrayAccess (at http://www.php.net/manual/en/class.arrayaccess.php) doesn't show it implementing Traversable. Nevertheless, you can still use any class you write that implements ArrayAccess in a foreach loop.
>
> This seems like an oversight in the documentation--unless I am missing something?
>

Not an oversight, IMHO. I think it's impossible for the document
writers to cover *every* possible usage.

That's why there are usage notes, contributed by users like yourself,
who have found other usages which are valuable (or do not work).

You can always add your own note to the documentation to show how it's
done; in fact I would encourage it.

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Re: ArrayAccess interface, Traversable interface and foreach [message #185989 is a reply to message #185987]

Sat, 24 May 2014 06:05

Christoph Michael Bec
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kurtk(at)pobox(dot)com wrote:

> The documentation for ArrayAccess (at
> http://www.php.net/manual/en/class.arrayaccess.php) doesn't show it
> implementing Traversable. Nevertheless, you can still use any class
> you write that implements ArrayAccess in a foreach loop.
>
> This seems like an oversight in the documentation--unless I am
> missing something?

You can use any object (whether it is an instance of a class that
implements Traversable or not) in a foreach loop, see
<http://www.php.net/manual/en/control-structures.foreach.php>.

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Christoph M. Becker

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Re: ArrayAccess interface, Traversable interface and foreach [message #185990 is a reply to message #185989]

Sat, 24 May 2014 07:09

Jerry Stuckle
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On 5/24/2014 6:05 AM, Christoph Michael Becker wrote:
> kurtk(at)pobox(dot)com wrote:
>
>> The documentation for ArrayAccess (at
>> http://www.php.net/manual/en/class.arrayaccess.php) doesn't show it
>> implementing Traversable. Nevertheless, you can still use any class
>> you write that implements ArrayAccess in a foreach loop.
>>
>> This seems like an oversight in the documentation--unless I am
>> missing something?
>
> You can use any object (whether it is an instance of a class that
> implements Traversable or not) in a foreach loop, see
> <http://www.php.net/manual/en/control-structures.foreach.php>.
>

But that is an entirely different access to what Kurt is talking about.

Kurt is discussing how to transverse an array within an object; your
page discusses how to transverse public data members in an object. But
good OO practices says all data members should be private.

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Re: ArrayAccess interface, Traversable interface and foreach [message #185991 is a reply to message #185990]

Sat, 24 May 2014 08:37

Christoph Michael Bec
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Jerry Stuckle wrote:

> On 5/24/2014 6:05 AM, Christoph Michael Becker wrote:
>> kurtk(at)pobox(dot)com wrote:
>>
>>> The documentation for ArrayAccess (at
>>> http://www.php.net/manual/en/class.arrayaccess.php) doesn't show it
>>> implementing Traversable. Nevertheless, you can still use any class
>>> you write that implements ArrayAccess in a foreach loop.
>>>
>>> This seems like an oversight in the documentation--unless I am
>>> missing something?
>>
>> You can use any object (whether it is an instance of a class that
>> implements Traversable or not) in a foreach loop, see
>> <http://www.php.net/manual/en/control-structures.foreach.php>.
>>
>
> But that is an entirely different access to what Kurt is talking about.
>
> Kurt is discussing how to transverse an array within an object; your
> page discusses how to transverse public data members in an object. But
> good OO practices says all data members should be private.

To traverse an array which is a member of an object $o with foreach($o
....), the object's class has to implement IteratorAggregate or Iterator,
not ArrayAccess.

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Christoph M. Becker

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Re: ArrayAccess interface, Traversable interface and foreach [message #185996 is a reply to message #185989]

Tue, 27 May 2014 14:59

Adam Harvey
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On Sat, 24 May 2014 12:05:02 +0200, Christoph Michael Becker wrote:

> kurtk(at)pobox(dot)com wrote:
>
>> This seems like an oversight in the documentation--unless I am missing
>> something?
>
> You can use any object (whether it is an instance of a class that
> implements Traversable or not) in a foreach loop, see
> <http://www.php.net/manual/en/control-structures.foreach.php>.

Yep, this is why objects that implement ArrayAccess still work with
foreach without implementing Traversable.

ArrayAccess and Traversable are technically different things: Traversable
provides a way to control iteration, whereas ArrayAccess is only for
array-style dereferencing via $object['key']. In practice, classes that
need to imitate arrays will need to implement both (probably by extending
a class such as ArrayObject that implements both interfaces).

Adam

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Re: ArrayAccess interface, Traversable interface and foreach [message #186028 is a reply to message #185989]

Mon, 02 June 2014 10:15

kurtk(at)pobox(dot)com
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> You can use any object (whether it is an instance of a class that
>
> implements Traversable or not) in a foreach loop, see
> <http://www.php.net/manual/en/control-structures.foreach.php>.

Thanks Christoph. I didn't realize that any object can be used in a foreach loop, and that it doesn't need to implement an interface that derives from Traversable.

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