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

[dan frost]

The main problem with XCLASSes in TYPO3 is the lack of a separation of 
concerns - people are extending one class for several reasons. There 
should be several classes.

Nice idea though - have you come across Aspect Oriented Programming? 
Might make things easier...

dan


Kraft Bernhard wrote:
> 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