MATLAB: discover restricted class of properties

Question

MATLAB R2016a introduced a documented mechanism for restricting the class of the properties of an object (I'm aware that there's also an older, different, undocumented way to do that, but I'm not using that method). For example:

classdef MyClass
    properties
        myProperty RestrictedClass
    end
end

will restrict the property myProperty so that its values must be of class RestrictedClass.

If you've implemented such a class, is there a way to use MATLAB's class metadata interface to programmatically discover the class of the restricted property?

I was hoping that if I used

m = ?MyClass;
p = m.PropertyList(1);

then the metaproperty object p would contain information about the class to which it was restricted - but it seems not.

Is there a way to programmatically discover it? The method would need to not involve actually instantiating the class - both because that might have side effects, and also because it would need to work with Abstract classes.

PS Also not involving anything gross like parsing the source code of the class. Imagine that I might like to do this with a class whose source code had been obfuscated using pcode.

Answer 1

You can use the undocumented hack of converting an object to a structure in order to inspect the non-public properties of the object. The meta.Property objects contain a hidden meta.Validation object property, which has the validation information for the property:

  Validation with properties:

                 Class: [1×1 meta.class]
                  Size: [1×0 meta.ArrayDimension]
    ValidatorFunctions: {1×0 cell}

With a given example class:

classdef SOcode
    properties
        myProperty1 double
        myProperty2 struct
    end
end

We can inspect the meta.PropertyList to locate the values we need:

>> test = struct(codemeta.PropertyList(1))

test = 

  struct with fields:

                    Name: 'myProperty1'

                    ... snip ...

                    Type: [1×1 meta.type]
              Validation: [1×1 meta.Validation]
           DefiningClass: [1×1 meta.class]

                    ... snip ...

We can then do something like the following:

codemeta = ?SOcode;

nprops = numel(codemeta.PropertyList);
validationclass = cell(nprops, 1);

for ii = 1:nprops
    validationclass{ii} = codemeta.PropertyList(ii).Validation.Class.Name;
end

And receive:

>> validationclass

validationclass =

  2×1 cell array

    {'double'}
    {'struct'}