On dependent properties: Is this poor Object Oriented Programming?

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Hi, I have a class C1 with a dependent property d and another class C2 which inherits from C1.
When property d is called from C2, it naturally goes through C1. I would like the d coming from C2 to be a transformation of the d coming from C1.
What I did is to create an auxiliary function (not a new method) that is called by C1. The function does what C1 would do to get d and then checks whether the input is a C2 object in which case it transforms d.
Is this bad programming? Would you do it differently?
Thanks,

Accepted Answer

Adam
Adam on 18 Aug 2014
Edited: Adam on 19 Aug 2014
I would usually use the idea of a protected function that extends the base class.
So the base class function is of the type:
function d = get.d( obj )
% base class implementation here
d = doGetD( obj, d )
end
with an empty protected implementation of doGetD in the base class and an implementation that extends the base class in the derived class.
  2 Comments
Patrick Mboma
Patrick Mboma on 18 Aug 2014
Edited: Patrick Mboma on 18 Aug 2014
Besides the fact that one has to modify the base class, this definitely works. GREAT THANKS !!!
I ended up doing the following
classdef C1
properties(dependent)
d
end
methods
function d=get.d(this)
d=first_pass(this);
d=doGetD(this,d);
end
function d=doGetD(~,d)
end
end
end
classdef C2 < C1
methods
function d=doGetD(~,d)
d=transform(d);
end
end
end
Guillaume
Guillaume on 19 Aug 2014
Edited: Guillaume on 19 Aug 2014
You really should move your doGetD into a protected block just as in my example.

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More Answers (1)

Guillaume
Guillaume on 18 Aug 2014
No, it's not very good as your base class C1 now contains implementation that belongs to the derived class C2.
Rather than calling an auxiliary function in C1 d getter, you should call a private class method, that you then override in class C2.
  4 Comments
Patrick Mboma
Patrick Mboma on 18 Aug 2014
Thanks Guillaume,
There is nowhere I can see that d is first processed in C1 and then transformed in C2. Any workaround or maybe I am missing something?
per isakson
per isakson on 25 Aug 2014
Edited: per isakson on 25 Aug 2014
"There is nowhere I can see" &nbsp Use the "debugger" to step through the code and you will see that it works automagically.

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