How to synchronise inherited properties of class

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Tim Hattrell
Tim Hattrell 2019 年 10 月 14 日
コメント済み: Tim Hattrell 2019 年 10 月 17 日
I have a superclass TubeClass with a number of properties, one of which is outsideDiameter. From this superclass, I derive two subclasses, StraightTubeClass and BentTubeClass. Both of these classes inherit the property outsideDiameter. So far so good...
I would now like to create a third class, UTubeClass, which again inherets from TubeClass. Now, UTubeClass comprises two straight legs of tube and a 180° bend. It also inherits the outsideDiameter property. So now I have a construction something like
MyUTube = UTubeClass; % Make new U-tube object
MyUTube.outsideDiameter = 100
MyUTube.someOtherProperties = 'foo'
MyUTube.straightLeg.outsideDiameter = 100
MyUTube.bend.outsideDiameter = 100
Ideally the outsideDiameter property would be the same in all places. I can figure out how to create a set method for UTubeClass such that when I set the property of outside diameter it is synchronised across all three usages, eg
MyUTube = UTubeClass;
MyUTube.outsideDiameter = 500;
% results in...
MyUTube.outsideDiameter = 500
MyUTube.straightLeg.outsideDiameter = 500
MyUTube.bend.outsideDiameter = 500
However, it is still possible to break this and independently set the value of the straight leg or bend outside diameter, eg
MyUTube = UTubeClass;
MyUTube.outsideDiameter = 500;
% results in...
MyUTube.outsideDiameter = 500
MyUTube.straightLeg.outsideDiameter = 500
MyUTube.bend.outsideDiameter = 500
% however...
MyUTube.straightLeg.outsideDiameter = 1000; % makes no sense, because now the OD is out of synch with the other values
So, is there a way to prevent this behavour, or should I be approaching the problem differently.

採用された回答

Jeff Miller
Jeff Miller 2019 年 10 月 15 日
I would say your UTubeClass should not descend from TubeClass. It's not the case that UTube "is a" Tube, but rather than UTube "has a" tube (or, really, it has two of them--one bent and one straight).
Another way to say it is that the UTube does not have its own independent diameter, separately from the diameters of its component straight and bent tubes, so there shouldn't be a separate property for UTube.outsideDiameter.
  2 件のコメント
Tim Hattrell
Tim Hattrell 2019 年 10 月 17 日
Thanks for your kind advice. I'll refactor and see where I get to. PS - sorry for not responding sooner. The email notifications telling me that this thread was being commented on were getting filtered out as spam.

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