[CentralOH] Delegate Property

[Sam Corder]

Properties really shouldn't be doing calculations.  It hides the complexity
of an object.  Instead you lean toward explicit method invocations with
names that imply some work is being done such as calculate_sales_tax.
 Conversely if your object is more just a data structure without behavior it
would be acceptable to have a sales_tax property where the value was just
stored and retrieved.  It is a Single Responsibility Principle (SRP)
violation to be both data structure and behavior oriented.

On Sat, Oct 9, 2010 at 12:38 AM, Mark Erbaugh <mark at microenh.com> 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
>         doc = """Docstring""" #@UnusedVariable
>
>
>         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
>
>
>
>
> class B(object):
>
>
>     def __init__(self):
>         self.w = W()
>
>
> 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.
>
> Thanks,
> Mark
>
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>
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