Variable YYY originally saved as a XXX cannot be instantiated as an object and will be read in as a uint32

Question

I've made a mistake and recorded a bunch of important data using a class definition that I can't find anymore. The methods are not important, I just want the data; a struct conversion would be fine.

Is there any way I can recover this?

Googling it did not help.

Answer 1

The solution is to create a new class that overloads the loadobj method. See here for more information regarding the load process for classes.

I replicated your problem by creating a class:

classdef myclass
   properties
      Prop1
      Prop2
      Prop3
   end
   methods
       function obj = myclass(a,b,c)
           obj.Prop1 = a;
           obj.Prop2 = b;
           obj.Prop3 = c;
       end
   end
end

Then I created an object of this class and saving it to a file "x.mat":

x = myclass('a',56,[1,2,3]);
save x

Next, I deleted the myclass file and did clear classes. This put me in your situation.

I then created a new myclass class that overloads the loadobj method:

classdef myclass
   properties
       data
   end
   methods (Static)
       function obj = loadobj(s)
           obj = myclass;
           obj.data = s;
       end
   end
end

Note how it doesn't know any of the original properties. This does not matter. If any of the original properties is missing when loading an object from a MAT-file, loadobj will be called with s being a struct containing all the properties of the original object.

With this new class definition, load x created an object x of class myclass, where x.data was a struct containing the properties of the object saved in "x.mat".