How to set a protected superclass property from subclass method?

I have an abstract superclass with some protected properties. I have a subclass with a set method that takes name-value pairs of the superclass and subclass and assigns them. However, when i call the set method from an instance of the subclass, I cannot set the superclass properties as Matlab gives an error saying that the name-values must be properties of the subclass.

For example:

m = MVA();

m.set('Events',struct('A',1,'B',2)); % works fine since Events is a property of MVA

m.set('analysisCycle','Test'); % does not work and errors saying that analysisCyle must be a property of MVA. this is even though analysisCycle is a protected property

Setting the analysisCycle proeprty from an instance of MVA works when the superclass property is public. However, I'd like to not have it public.

How can I set a superclass protected property from an instance of a subclass? The issue might have to do with how property validate the inputs of my set method in the sublass (eg, propertyArguments.?MVA). However, I beleive this should still give access to protected superclass properties.

Answer 1

[Matt J]

You cannot use the ?.MVA syntax on non-public properties. Since you already have validation in the base class, I don't think you need it in your set() method or MVA() constructor as well. I would just do,

        function obj = set(obj,varargin)
            %SET    Set property value.
            % Syntax:
            %   obj.set(Name,Value)
      
            propertyArguments=struct(varargin{:});

            fieldNames = fieldnames(propertyArguments);
            for i = 1:numel(fieldNames)
                propName = fieldNames{i};
                obj.(propName) = propertyArguments.(propName);
            end

            obj.modifiedBy = getUser();
            obj.modifiedDate = datetime("now");
            
        end   

[Chris Nemecek]

That makes sense. But, is there a way I can validate that the "fieldNames" are valid properties of DataClass or MVA? Otherwise, the function will error if can't assign obj.(propName). I'm just trying to more "gracefully" error if the function doesn't get correct inputs.

Also, would it be better to use an arguments (Repeating) block instead of varargin so that at least you have name-value pairs and not an odd number of inputs by mistake?

[Matt J]

Yes, you can do all that.

        function obj = set(obj,fieldNames,values)
            %SET    Set property value.
            % Syntax:
            %   obj.set(Name,Value)
            arguments
                obj
            end
            arguments (Repeating)
             fieldNames char
             values
            end

            mc=?DataClass; 
            validprops ={mc.PropertyList.Name};

           assert( all(ismember(fieldNames, validprops)),...
                      'Invalid name-value pair');


            for i = 1:numel(fieldNames)
                obj.(fieldNames{i}) = values{i};
            end

            obj.modifiedBy = getUser();
            obj.modifiedDate = datetime("now");
        end  

[Chris Nemecek]

This would only check for DataClass properties, right? Wouldn't it error if you had an MVA property?

mc=?DataClass;

validprops ={mc.PropertyList.Name};

assert( all(ismember(fieldNames, validprops)),...

'Invalid name-value pair');

Wouldn't you need to do something else to error check for MVA properties? And then some kind of OR logic to discern between DataClass and MVA properties?

[Matt J]

This would only check for DataClass properties, right? Wouldn't it error if you had an MVA property?

Yes, but it's an easy modification,

mc=?MVA; validprops ={mc.PropertyList.Name};

Now, validprops will contain all MVA properties, including those inherited from DataClass.

Wouldn't you need to do something else to error check for MVA properties? And then some kind of OR logic to discern between DataClass and MVA properties?

So, no. In light of the above, I don't see a real need for that. If for some reason, you needed to distinguish between properties based on whether or not they were inherited from DataClass, you could construct a table or dictionary giving the DefiningClass of each property, e.g.,

mc=?MVA; 
pl =mc.PropertyList;
T=table(string({pl.Name}'), arrayfun(@(z)string( z.Name),[pl.DefiningClass]'))

T =

8×2 table

Var1 Var2

_______________ ___________

"data" "MVA"

"Events" "MVA"

"analysisCycle" "DataClass"

"dataLog" "DataClass"

"modifiedBy" "DataClass"

"modifiedDate" "DataClass"

"createdBy" "DataClass"

"createdDate" "DataClass"