[Typo3-dev] [Good||Silly] idea ???

[Kraft Bernhard]

Hallo list,


Since I know about XCLASSes and how they work I was looking for a method to extend classes
in a more clever way than until now.

Because at the moment a extensio can extend a core class, but if the core-class is already extended
by another extension those two extensions won't work together and the last one installed will
take precedence.

But if those two extensions modify completly different functions from the base class they could
exist together...

The only workaround at the moment is that one extension knows about the other one and extends the
extension-class instead of the core class.

-----

The main problem when doing XCLASS extensions is that the classname of the extending class must be
set to a static value. If the classname could be a dynamic value the complete problem would be solved.
I tried:
$classname = 'baseclass';
and
define('CLASSNAME', 'baseclass');
but none of them did work ...

After investigating a little further and asking on some mailing lists I came to the following POSSIBLE
solution:
write the class definition in an extra file without leading "<?php" and trailing "?>" tags.
then load this file via  "implode('', file($filename))".
then replace the markers for baseclass and extended class.
then evalute the script.

Here are some sample scripts which show what I tried (and worked !!):
-------------------------<index.php>------------------------------------
<?php
define('TYPO3_MODE', 'FE');
// Those lines should be in ext_localconf.php of the extensions
$TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS2']['t3lib/class.t3lib_testphp.php'][] = 'extend1.php';
$TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS2']['t3lib/class.t3lib_testphp.php'][] = 'extend2.php';

class baseclass {
    function a() {
       echo 'I\'m function "a" from base class !<br>'.chr(10);
    }
    function b() {
       echo 'I\'m function "b" from base class !<br>'.chr(10);
    }
    function c() {
       echo 'I\'m function "c" from base class !<br>'.chr(10);
    }
}
function &makeInstance($className)  {
    return class_exists('ux_'.$className) ? makeInstance('ux_'.$className) : new $className;
}
// XCLASS2 inclusion
if (defined('TYPO3_MODE') && is_array($TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS2']['t3lib/class.t3lib_testphp.php']))  {
    foreach ($TYPO3_CONF_VARS[TYPO3_MODE]['XCLASS2']['t3lib/class.t3lib_testphp.php'] as $inc)   {
       include_once($inc);
    }
}
// Main
$main = makeInstance('baseclass');
$main->a();
$main->b();
$main->c();
?>
-------------------------</index.php>------------------------------------

-------------------------<extend1.php>------------------------------------
<?php
$basename = 'baseclass';
$extname = 'ux_baseclass';
while (class_exists($extname)) {
    $basename = 'ux_'.$basename;
    $extname = 'ux_'.$extname;
}
$data = implode('', file('extend1_code.php'));
$data = str_replace('###EXT_CLASS###', $extname, $data);
$data = str_replace('###BASE_CLASS###', $basename, $data);
eval($data);
?>
-------------------------</extend1.php>------------------------------------


-------------------------<extend1_code.php>------------------------------------
class ###EXT_CLASS### extends ###BASE_CLASS### {
    function a() {
       echo 'I\'m function "a" from extend1 class !<br>'.chr(10);
    }
}
-------------------------</extend1_code.php>------------------------------------


-------------------------<extend1.php>------------------------------------
<?php
$basename = 'baseclass';
$extname = 'ux_baseclass';
while (class_exists($extname)) {
    $basename = 'ux_'.$basename;
    $extname = 'ux_'.$extname;
}
$data = implode('', file('extend2_code.php'));
$data = str_replace('###EXT_CLASS###', $extname, $data);
$data = str_replace('###BASE_CLASS###', $basename, $data);
eval($data);
?>
-------------------------</extend1.php>------------------------------------


-------------------------<extend1_code.php>------------------------------------
class ###EXT_CLASS### extends ###BASE_CLASS### {
    function b() {
       echo 'I\'m function "b" from extend2 class !<br>'.chr(10);
    }
}
-------------------------</extend1_code.php>------------------------------------


After calling index.php the follwing gets outputed:
-------------------------<output>----------------------------------------
I'm function "a" from extend1 class !
I'm function "b" from extend2 class !
I'm function "c" from base class !
-------------------------</output>----------------------------------------


So is this a good idea and should we think about a new (possible different) way of doing XCLASS
extending ???

Or is this "eval" thingy just damn slow and one shouldn't use it ?

Or are there any other reasons why such a style isn't good practice ?

This way of XCLASSing would also eliminate the problem to have the same code in two locations when
you extend two different baseclasses (i.E. class.t3lib_stdgraphic, class.tslib_gifbuilder) with the
same code ... (as you would just have to include the same file in two locations and change the classnames
accordingly)


greets,
Bernhard
-- 
Kraft Bernhard
MOKKA Medienagentur <http://www.mokka.at>
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