When subclassing "double" with new properties, is there an easy way to access the data value?

Say I have a class subclassing double, and I want to add a string (Similar to the 'extendDouble' in the documentation). Is there an easy way to access the actual numeric value without the extra properties, particular for reassigning? Or if I want to change the value, will I have to recreate the value as a new member of the class with the new value and the same string?

e.g.

classdef myDouble < double

properties
    string
end

methods 
    function obj = myDouble(s)
        % Construct object (simplified)
        obj.string = s;
    end
end

end

----------

x = myDouble(2,'string')

x = 

    2 string
    
x = 3

x = 

    3 string
    

Answer 1

[Jeffrey Clark]

@Robbie, see Subclasses of Built-In Types with Properties - MATLAB & Simulink (mathworks.com)

Sorry but the subsasgn and subsref will be needed (and maybe numArgumentsFromSubscript) just follow the example given, or use Customize Object Indexing - MATLAB & Simulink (mathworks.com) for MATLAB 2021b+ preferred pattern (but it isn't any easier or closer to what you really want).

It would be easier to not subclass a basic type, just have two properties for the string and numeric. Then when referencing the obj.property you get all the appropriate property functions like sqrt(x.val) and disp(['string is ' x.str]), but x = 3 would have to be done as x.val = 3

Answer 2

[Aaron Kaw]

Try

x = myDouble(2,'string')
double(x)

I like to also add the following non-static method to my double subclasses:

function value = double(instance)
    value = builtin('double', instance);
end

so that I can do

y = myDouble(2, 'string').double

if I only cared about the double value the class outputed for the particular usage of myDouble.