Function referring to abstract class

Hi

I'm looking to use an abstract class to represent a generic "interface" (texture) on a solar cell surface.

A "cell" object is made up of "layers" which each have a top and bottom interface:

classdef ct_layer < handle  
properties
        t;                  % layer thickness
        n;                  % real refractive index
        k;                  % imaj refractive index

          interfaceT = ct_interface.empty % Top and Bottom interface
          interfaceB = ct_interface.empty

where I want ct_interface to be the abstract class, so that I can go and make plannar interfaces or pyramidal interfaces or whatever later. I want to do it like this because not every layer needs to have an interface assigned -- it might just pick up those from adjacent layers when the cell is "assembled"

However I can't preset the "type" of interface if ct_interface is abstract, and it defaults to double[] otherwise (such that I can't add the interfaces when the time comes).

I've tried reading through all the docs without resolution, but I get the sense I'm thinking about this incorrectly.

Cheers in advance for any suggestions

Leon

Answer 1

[Jacob Halbrooks]

Your problem description suggests to me that you might want to structure your classes according to the Strategy design pattern with a special Null object concrete strategy. I would recommend you make a package to hold your Abstract class and its concrete children.

For example, create a package folder named +CTInterfaces containing Abstract, Null, Plannar, and whatever else. Your layer class could then use Null as the default:

properties
   interfaceT = CTInterfaces.Null;
   interfaceB = CTInterfaces.Null;
end

[Daniel Shub]

I like this. I have no formal training in OOP so learning the proper terminology is helpful. I am having trouble relating the general concept of null to the MATLAB concept of empty. Does it make sense to make an array of null objects? Should isempty(CTInterfaces.Null) always return true?

[Jacob Halbrooks]

Think of the Null object as one that can be called just like any other CTInterfaces object, except it performs no work. That is, CTInterfaces.Null would be a class that overrides all of the necessary methods (that are defined as Abstract in CTInterfaces.Abstract), but the methods would have no code.

[Leon]

Man you guys work fast! Thanks for both the suggestions, I've gone ahead with an interfaces folder and null/empty interface. Works exactly as intended (so far!).

Answer 2

[Daniel Shub]

I think the key piece is:

not every layer needs to have an interface assigned -- it might just pick up those from adjacent layers when the cell is "assembled"

I think you need to define a concrete class of ct_interface_none which is a subclass of the abstract ct_interface. The ct_interface_none class would then take care of picking up the information from the adjacent layers and deal gracefully with being in isolation..