I also don't really get the idea of interface and abstract classes ? They
don't seem to be any practical use ? Maybe that's me ? Anyway, not really
relevant to this post ...
there is a lot of usefulness in these constructs; look into design patterns.
also, there are code libraries already written w/ the abstraction you are
trying to develop.
im not discouraging you from developing your own, but it may be helpful for
you to study some of the other code.
check out
http://pear.php.net/package/MDB2
http://ez.no/doc/components/view/2007.1/(file)/classtrees_Database.html
http://www.onphp.org/doxy/trunk/
-nathan
ps.
i believe interjinn provides a db layer as well :>
On 7/11/07, Steve Perkins <sp@xxxxxxxxxxxx> wrote:
OK, so that came out fairly illegible. Try again:
Hi, new to PHP5 (and the forums evidently !) and I have a question about
the
object model.
I want to be able to create a class which is allows abstraction from
specifics. So for one example, imagine a generic database connection
wrapper
which can have multiple drivers depending on the database used. Some of
the
functionality is generic, some is database specific (mysql_ , odbc_). So:
Class MySQL_driver {
public prop1 ;
public connect() {
echo "Foo";
}
public runquery() {
echo "Foo";
}
...
}
Class ODBC_driver {
public prop1 ;
public connect() {
echo "Foo";
}
public runquery() {
echo "Foo";
}
...
}
Class generic {
public $driver = null ;
function __construct($connection_type) {
if $this->connection_type = "MySQL" {
$this->driver = new MySQL_Driver ;
} else {
$this->driver = new ODBC_Driver ;
}
}
// Using the non-generic connect() from the selected driver
function authenticate {
$this->driver->prop1 = "fooey"
// These references work fine from within
// the generic class
echo $this->driver->prop1 ;
echo $this->driver->function1 ;
}
// Report non-generic errors from the selected driver
function errors {
}
function debug {
}
...
}
$gen = new generic("MySQL") ;
// Instantiate the generic database object, which
// determines its own driver
$gen->driver->prop1 = "fooey"
// but they fail from here
echo $gen->driver->prop1 ;
echo $gen->driver->function1 ;
// this works ok though, so everything is created
// correctly
$gen->authenticate() ;
So I want to access generic functions as $generic->authenticate(), and
database specific functions $generic->driver->runquery. This allows the
top
level code to be able to be completely generic and not know anything about
the underlying database.
But I can't ! I can't find a way of accessing the encapsulated object
(driver) from the instantiator of generic. Is it possible ?
I guess there are lots of "workaround" ways. I could write lots of
"middleman" code in generic and use things like __set and __get etc but
its
lots of extra overhead. I also know I could use extends but that makes the
code the wrong way around (MySQL_Driver would have to extend generic),
hence
the top-level application would have to include code to determine which
driver to create rather than the db object determining its own connection
driver to use. This is true also for just lumping everything in a single
class per db type.
Surely it must be possible ? Or am I missing something ?
I also don't really get the idea of interface and abstract classes ? They
don't seem to be any practical use ? Maybe that's me ? Anyway, not really
relevant to this post ...
Please, please can someone help !!
Thanks
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