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Posted by Thomas Hochstetter on 10/02/07 11:15
Thanks, will do ;-) (as of this mail)
-----Original Message-----
From: Jochem Maas [mailto:jochem@iamjochem.com]
Sent: 06 May 2005 03:08 PM
To: Thomas Hochstetter
Cc: [php] PHP General List
Subject: Re: [PHP] Array of objects
Thomas Hochstetter wrote:
> Hi Jochem,
>
> Thanks for that. The eval story was just a desperate attempt ... anyway, I
> know references a bit from my c++ times. I am not sure how that will help
in
> this case though. Maybe you want to share with me your thoughts on that.
well compare:
$a =& new Test; // $a is the new object
$b = new Test; // $b is a copy of the new object
$c =& $b; // $c refers to the same object
$d = $b; // $d is a seperate copy of $b
by default in php4 every time you assign an object (new or otherwise) to
a variable you are making a COPY, the same goes for when you pass an object
to a function.
There is shedloads of info around that explains the how & why of references
in detail, just google around a bit.
I have no idea about c++ (the C++ book beside the bed is only half-read and
hardly understood ;-) so whether your understanding of references in c++ is
a
help or hinderance I can guess at :-)
>
> Just for completion's sake:
>
> I want to have an array in a config file that holds all possible modules
> that can be loaded. The module name comes from the url string and if the
> string is not in that array I display a default page (so no tinkering can
go
> on).
> The reason for doing what you helped me doing now is only a cosmetic
reason.
> Instead of having to declare another block with if and else if statements
to
> instantiate the objects as in:
>
> if( $Site == null ) {
> if ( $module=="browse" ) { $Site = new
> Browse(); }
> else if ( $module=="details" ) { $Site = new Details();}
> }
>
> I thought it would be cool to be able to instantiate the object when I
check
> the array (on finding the right entry).
I might have written that as a function e.g.
function getModule( $modName )
{
if (in_array($modName, $modules)) {
$modClass = $modules[ $modName ];
return new $modClass();
}
return new DefaultModule();
}
or possible a switch statement, which would be a more concise way of
writing a big if/else block
switch ($_GET['module']) {
case 'browse':
$Site = new Browse();
break;
case 'details':
$Site = new Details();
break;
default:
$Site = new DefaultModule();
break;
}
.... or a combination of the two (examples above).
btw, there is nothing implicitly wrong with the boring old if/else block...
it just maybe doesn't have the coolness factor, regardless eval() really
doesn't
sound like the way to go here at all. which ever way you do it, the most
important
thing is to layout you code _neatly_ (don't be afraid of using a bit of
space :-)
and comment as much as possible so that maintainance of the code is as easy
as
possible.
Good Luck! :-)
PS - please reply to list as well - somebody might be interested (and learn
something).
>
> Thanks again.
>
> Cheers
>
> Thomas
>
> -----Original Message-----
> From: Jochem Maas [mailto:jochem@iamjochem.com]
> Sent: 06 May 2005 01:17 PM
> To: Thomas Hochstetter
> Cc: php-general@lists.php.net
> Subject: Re: [PHP] Array of objects
>
> Thomas Hochstetter wrote:
>
>>Spiraleye.Studios
>>
>> Hi there,
>>
>>I need help with arrays. What I want to do is to have an array of the
>>following structure:
>>
>>$mod=array( 'name'=>new NameObject());
>
> ^ -- looks like your single quotes got mangled in my email
> client.
>
> class Test { function Test($str = '') { echo $str; } }
>
> $_GET['module'] = 'testmod';
> $mod = array( 'testmod' => 'Test' );
>
> if (isset($mod[$_GET['module']]) && class_exists($c =
> $mod[$_GET['module']])) {
> $Site = new $c;
> // $Site = new $c('Testing');
> } else {
> die ('Can't create module object');
> }
>
>
> ... and if that doesn't give you the knowledge/inspiration/lighbulb-moment
> to fix whatever it is your trying to do then please mail the list again
> and explain what _and_ why you are trying to do whatever it is you're
trying
> to
> do (this helps people to understand thereby having a better chance of
> offering some helpful advice!)
>
>
>>Then later in the page I want to go $Site = $mod[$_GET['module']] (or
>>something like that) to instantiate a new object.
>>
>>The problem is, if done the way above it will try to instantiate the
>>object right there and then in the array (defeating the purpose), if I
>>put it in quotes and try to use something like:
>>
>>(object)eval($mod[$_GET['module']]) it does not instantiate the object.
>
>
> well assuming no syntax error occurs (eval will return false is such a
case)
> then I bet it actually does, only your eval statement isn't assigning the
> new object to anything!... besides which you are casting the return
> value of eval to an object which is pointless for 2 reasons:
>
> 1. casting NULL to an object gets you nowhere (atleast not in this case)
> 2. casting an object to an object get you... nowhere :-)
>
> so....:
>
> $mod = array( 'name' => 'return new NameObject()');
> $Site = eval($mod['name']);
>
> PS - do you know what a reference is? (in terms of [php] variables)?
> understanding
> references with regard to objects (especially if your using php4) is a
> really
> good addition to your coding arsenal (it will save you time hunting
> inexplicable bugs -
> often such 'bugs' are nog longer inexplicable! and allow you to increase
the
> speed of your
> code)
>
> PPS - using eval() is hardly ever the only option, and given that eval()
is
> very slow its best
> to avoid it at all costs (assuming there is another way to do what you
> want)... also eval()
> _can_ be a security risk, if you do something like:
>
> eval($_GET['command'])
>
> without santizing the contents of $_GET['command'], hopefully you can see
> why.
>
>
>
>>Is there a way to do this?
>>
>>Thanks
>>
>>Thomas
>>
>>*
>>**SPIRAL EYE STUDIOS ***
>>P.O. Box 37907, Faerie Glen, 0043
>>
>>Tel: +27 12 362 3486
>>Fax: +27 12 362 3493
>>Mobile: +27 83 258 2669
>>Email: info@spiraleye.co.za <mailto:info@spiraleye.co.za>
>>Web: www.spiraleye.co.za <http://www.spiraleye.co.za>
>>
>>
>>
>
>
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