[CentralOH] Delegate Property

[Mark Erbaugh]

On Oct 9, 2010, at 12:38 AM, Mark Erbaugh wrote:

> Is there a way to delegate a read/write property in a class instance to a read/write property in a different class's instance that is a data member of the class? The only way I can think of is to assign the property getter and setter, but with some ways of creating properties, getters and setters aren't easily gotten.
> 
> i.e.
> 
> class W(object):
>     def a(): #@NoSelf
>        
>         def fget(self):
>             return self._a
>            
>         def fset(self, value):
>             self._a = value
>            
>         def fdel(self):
>             del self._a
>            
>         return locals()
>        
>     a = property(**a())
> 
>     def __init__(self):
>         self._a = 10
>         
> 
> I would like to have an 'a' property on B such that when read they read the a from the contained self.w and when written they write that a.  In this example, the property is just using a local variable, but in a real-world case, the property could be doing some computations.

I've come up with at least one solution that seems to work:

class B(object):
    
    def __init__(self):
        self.w = A()

    def a(): #@NoSelf
        fget = lambda self : self.w.a
        fset = lambda self,v : self.w.a.__set__(v)
        return (fget, fset)
       
    a = property(*a())
        


Mark

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/mailman/private/centraloh/attachments/20101009/ff84f7b8/attachment.html>