Immutable properties and subclass constructors

Is it possible to somehow set immutable superclass properties in a subclass constructor? It seems not, but maybe I'm just misinterpreting the documentation and error messages and this is possible somehow?

In case this doesn't make sense, my motivation is this: I've written a fairly nice data-analysis object that I use as a superclass all the time. It loads data from the data acquisition tool we normally use, and I have different subclasses for different experiments, which have different analysis requirements but most of the basics are the same (and located in the superclass).

Now I'd like to re-use all that code by loading data (of essentially the same form) but from a different filetype (new constructor required) into the properties expected by the superclass. I could just make the properties protected in the superclass (instead of immutable), but I'd really like them to only be changed within the constructor of the new subclass.

Or maybe I should be approaching this in a different way entirely?

Answer 1

[Matt J]

Thank you, but I should have rephrased my question - I was looking for a way to overwrite the value set by the superclass constructor.

I'm not sure why it would be preferable to overwrite when you can just set the value in the subclass constructor directly. Nevertheless, if you must do this, an alternative would be to convert your original immutable property (let's call it "immutableProp") to a Dependent property like in the following,

     classdef myclass

         properties (SetAccess=immutable)
          p;
         end

         properties (Dependent)

             immutableProp; %imitates an immutable property

         end

         methods 

             function obj=myclass(pValue)

                   obj.p=pValue;

             end

             function out=get.immutableProp(obj)

                 out = obj.accessIt;

             end

             function out=accessIt(obj)

                 out=obj.p;

             end

         end

     end

Then in your subclass, you simply overload accessIt() in a way that causes immutableProp to refer to q instead of p.

     classdef mysubclass<myclass

         properties (SetAccess=immutable)
         q;
         end

         methods 

             function obj=mysubclass(pValue, qValue)

                   obj=obj@myclass(pValue);
                   obj.q=qValue;

             end

             function out=accessIt(obj)

                 out=obj.q;

             end

         end

     end

[Christian Veenstra]

Clever, thanks.

Answer 2

[Matt J]

Is it possible to somehow set immutable superclass properties in a subclass constructor?

Yes. The subclass constructor can call the superclass constructor and use that to set the immutable property, e.g.,

     classdef myclass 

         properties (SetAccess=immutable)

            p;
         end

         methods  
             function obj=myclass(pval)
                 obj.p=pval;
             end

         end

     end

classdef mysubclass < myclass
     methods 
          function obj=mysubclass(pval)
              obj=obj@myclass(pval);
          end
     end
end

[Christian Veenstra]

Thank you, but I should have rephrased my question - I was looking for a way to overwrite the value set by the superclass constructor. For now I've just added an extra argument to my superclass constructor - when I set that flag it does something different and sets the values as expected by the subclass.

This "works", but it seems like a sloppy workaround - like essentially the code for my subclass has spread into the superclass.