[Tutor] Class in a class

[Liam Clarke]

Hi Kent, 

>So the layering is

>GUI - user interaction
>Application functionality
>CbDao - application-specific database access
>DbAccess - generic database access, easy to use
>JDBC connection - raw database access, not so easy to use

This sounds a lot like what I'm aiming for in a project, the layers &
objects passed up and down, are you able to provide an example of your
CbDao class for my learning edification?

(btw, is it Dao as in Lao Tzu?)

Regards, 

Liam Clarke


On Thu, 17 Feb 2005 23:27:11 -0000, Alan Gauld <alan.gauld at freenet.co.uk> wrote:
> 
> > Does it make sense to do this:
> 
> That depends on what you are trying to do!
> If its to make scrambled eggs thewn nope, no sense
> whatsoever, but if writing a programme storing an
> instance inside another instance is very common
> indeed! :-)
> 
> > In [2]: class AB:
> >    ...:     pass
> >    ...:
> > In [3]: a = AB()
> >
> > In [5]: class BC:
> >    ...:     def __init__(self, foo):
> >    ...:         self.foo = foo
> >
> > In [6]: b = BC(a)
> 
> Indeed you can even store a class inside an object:
> 
> class C:
>   def shout(self): print 'HELLO! from C'
> 
> class D:
>   def shout(self): print 'HELLO! from D'
> 
> class A:
>   def __init__(self,cls):
>     self.c = cls
> 
>   def speak(self):
>     print 'I'm an A but I have an object that says:'
>     self.c().shout()
> 
> a = A(C)
> b = A(D)
> 
> a.speak()
> b.speak()
> 
> More commonly a method of A could also be created that
> returned an instance of C with certain A specific values.
> 
> The point of the example being simply that you can quite reasonably
> pass any PYthon object to a class/instance and it can be stored
> and later used or returned.
> 
> You can see a practical example of storing a class reference
> within an object in my Games Framework, described in the book
> of my tutorial (and the code is on Useless Python).
> 
> HTH
> 
> Alan G
> Author of the Learn to Program web tutor
> http://www.freenetpages.co.uk/hp/alan.gauld
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
> 


-- 
'There is only one basic human right, and that is to do as you damn well please.
And with it comes the only basic human duty, to take the consequences.