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How to create an instance from a class name

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  How to create an instance from a class name "Leonardo Azpurua" <leonardo@exmvps.org> - 2012-04-21 20:53 -0430
    Re: How to create an instance from a class name Ross McKay <au.org.zeta.at.rosko@invalid.invalid> - 2012-04-22 12:23 +1000
      Re: How to create an instance from a class name "Leonardo Azpurua" <leonardo@exmvps.org> - 2012-04-22 09:43 -0430
    Re: How to create an instance from a class name "M. Strobel" <sorry_no_mail_here@nowhere.dee> - 2012-04-22 11:19 +0200
      Re: How to create an instance from a class name "Leonardo Azpurua" <leonardo@exmvps.org> - 2012-04-22 09:45 -0430

#5642 — How to create an instance from a class name

Hi,

I am working on a class to generate a report from specs contained in a user 
defined file.

A section on the file defines a form in which the user will input parameters 
for the report. This form may contain different kinds of INPUT items, namely 
FECHA (date), NUMERO (number), TEXT, SELECT, LISTA (select with multiple 
options) or CODIGO (an items code, with the ability to search by 
name/description). Each item is defieed in a class that knows how to parse 
the definitions and generate the corresponding HTML/Script code.

Each class name is made of a preffix ("procesador") plus the type of item 
(e.g. "procesadorFECHA").

Initially I used a switch statement in order to build each class:

switch ($token->value)
{
    case "TEXT":
        $proc = new procesadorTEXT();
        break;
    case "NUMBER":
        $proc = new procesadorNUMERO();
        break;
    ...
    default:
        die("Invalid INPUT type ...");
}
$proc->go($tokens, $lineNumber, $this->context);

I recall having read somewhere an example of PHP instantiatiting an object 
from a class name, but I forgot both the workings and the source of the 
example. I made a few attempts with ReflectionClass, but I couldn't find a 
solution, so this is what I did:

   $className = "procesador" . $token->value;
   $newFunc = create_function("", "return new " . $className . "();");
   $proc = $newFunc();
   $proc->go($tokens, $lineNumber, $this->laEmpresa);
   unset($newFunc);

It works, but I would like to know whether it will produce any unexpected 
behaviour when the component enters in production, and if there is a better 
(cleaner) way to do it.

Thanks.

--

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#5643

On Sat, 21 Apr 2012 20:53:58 -0430, Leonardo Azpurua wrote:

>I am working on a class to generate a report from specs contained in a user 
>defined file.
>[...]
>I recall having read somewhere an example of PHP instantiatiting an object 
>from a class name, [...]

$className = 'ExampleClass';
$instance = new $className;

Can be quite handy in Singletons, e.g.

$className = __CLASS__;
$instance = new $className;
-- 
Ross McKay, Toronto, NSW Australia
"Let the laddie play wi the knife - he'll learn"
- The Wee Book of Calvin

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#5654

"Ross McKay" <au.org.zeta.at.rosko@invalid.invalid> escribió en el mensaje 
news:nnq6p7p82l6kp0dh4uetmejte0l4umd7so@4ax.com...
> On Sat, 21 Apr 2012 20:53:58 -0430, Leonardo Azpurua wrote:
>
>>I am working on a class to generate a report from specs contained in a 
>>user
>>defined file.
>>[...]
>>I recall having read somewhere an example of PHP instantiatiting an object
>>from a class name, [...]
>
> $className = 'ExampleClass';
> $instance = new $className;
>
> Can be quite handy in Singletons, e.g.
>
> $className = __CLASS__;
> $instance = new $className;

That's why I couldn't find it.


Thanks! 

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#5649

Am 22.04.2012 03:23, schrieb Leonardo Azpurua:
> Hi,
> 
> I am working on a class to generate a report from specs contained in a user 
> defined file.
> 
> A section on the file defines a form in which the user will input parameters 
> for the report. This form may contain different kinds of INPUT items, namely 
> FECHA (date), NUMERO (number), TEXT, SELECT, LISTA (select with multiple 
> options) or CODIGO (an items code, with the ability to search by 
> name/description). Each item is defieed in a class that knows how to parse 
> the definitions and generate the corresponding HTML/Script code.
> 
> Each class name is made of a preffix ("procesador") plus the type of item 
> (e.g. "procesadorFECHA").
> 
> Initially I used a switch statement in order to build each class:
> 
> switch ($token->value)
> {
>     case "TEXT":
>         $proc = new procesadorTEXT();
>         break;
>     case "NUMBER":
>         $proc = new procesadorNUMERO();
>         break;
>     ...
>     default:
>         die("Invalid INPUT type ...");
> }
> $proc->go($tokens, $lineNumber, $this->context);
> 
> I recall having read somewhere an example of PHP instantiatiting an object 
> from a class name, but I forgot both the workings and the source of the 
> example. I made a few attempts with ReflectionClass, but I couldn't find a 
> solution, so this is what I did:
> 
>    $className = "procesador" . $token->value;
>    $newFunc = create_function("", "return new " . $className . "();");
>    $proc = $newFunc();
>    $proc->go($tokens, $lineNumber, $this->laEmpresa);
>    unset($newFunc);
> 
> It works, but I would like to know whether it will produce any unexpected 
> behaviour when the component enters in production, and if there is a better 
> (cleaner) way to do it.
> 
> Thanks.
> 
> --

Just take the classname as variable in the new Operator:

class clase1 {
  function buenos() {
    echo "Bon día!\n";
  }
}

class clase2 {
  function buenos() {
   echo "Buenos días!\n";
  }
}

foreach (array(1,2) as $v) {
    $cn = 'clase' . $v;
    $c = new $cn();
    $c->buenos();
}
#--------------------
Bon día!
Buenos días!


/Str.

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#5655

"M. Strobel" <sorry_no_mail_here@nowhere.dee> escribió en el mensaje 
news:9vi0pdF23nU1@mid.uni-berlin.de...

> Just take the classname as variable in the new Operator:
>
> class clase1 {
>   function buenos() {
>     echo "Bon día!\n";
>   }
> }
>
> class clase2 {
>   function buenos() {
>    echo "Buenos días!\n";
>   }
> }
>
> foreach (array(1,2) as $v) {
>     $cn = 'clase' . $v;
>     $c = new $cn();
>     $c->buenos();
> }
> #--------------------
> Bon día!
> Buenos días!

Too easy to be remembered!

Thanks, obrigado, gracias!

.

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