[DB-SIG] Inheriting from a DBAPI 2.0 Cursor Object

[Peter L. Buschman]

Chis:

Thanks so much.  I had been so focused on finding an inheritance solution ( 
difficult since the Connection and Cursor objects are not exposed
directly in DBAPI ) that I completely missed simply wrapping the relevant 
objects. DBAPI is not that complex, so wrapping the methods is not
that much extra code.

--Peter

At 10:56 AM 9/25/2003 -0700, Chris Cogdon wrote:

>On Thursday, Sep 25, 2003, at 09:52 US/Pacific, Peter L. Buschman wrote:
>
>>My connect() function is simply a wrapper around the underlying driver's 
>>connect method that is smart enough to know
>>what driver it is talking to and what parameters to use.  The object 
>>returned is simply one of that driver's connection objects.
>>
>>How would I best define my own connection and cursor objects such that I 
>>can inherit from the underlying driver but also
>>override those few methods like execute to make the driver access as 
>>transparent as possible?
>
>The 'connect' function would need to return one of your OWN object types, 
>which can either 'wrap' or 'inherit' from the real type. Once you do that, 
>then you can define all the methods how you please, even if its just to 
>call the wrapped object (or, if you're inheriting, you can just omit it).
>
>For example, here's a rough outline of how I'd do it myself:
>
>In 'driver'
>
>def new ( connection_type ):
>         if connection_type = "mxodbc":
>                 return MxodbcDriver ()
>
>class MxodbcDriver:
>
>         def connect ( self, *argc, **argk ):
>                 return MxodbcWrapper ( db ):
>
># although, I dont know why you'd want to do it the above way... you could 
>always specifiy BOTH the database type, and the arguments, in the 'new' 
>function.
>
>
>class MxodbcWrapper:
>
>         def __init__ ( self, *argc, *argk ):
>                 self.db = mxodbc ( *argc, **argk )
>
>         def cursor ( self ):
>                 # do wrapper specific stuff
>                 return MxodbcCursor ( self )
>
>
>class MxodbcCursor:
>
>         def __init__ ( self, wrapper, cursor ):
>                 self.wrapper = wrapper
>                 self.cursor = self.wrapper.db.cursor () # This gets the 
> real DB's cursor
>
>         def execute ( self, args ):
>                 # self.wrapper can be used to get access to the wrapper, 
> or underlying DB
>                 # self.cursor can be used to get to the real cursor
>
>                 # wrapper specific stuff
>
>                 self.cursor.execute ( args )
>
>
>
>--
>    ("`-/")_.-'"``-._        Chris Cogdon <chris at cogdon.org>
>     . . `; -._    )-;-,_`)
>    (v_,)'  _  )`-.\  ``-'
>   _.- _..-_/ / ((.'
>((,.-'   ((,/   fL
>
>
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