Convert a class to structure and store in a .mat file - MATLAB

Question

I have a class which has some properties that they are objects of other classes, when I convert the class to a struct and check the data, the full information of all properties exist. but after storing it to a .mat file, when I load the data, the properties which are instances of other classes are disappeared! the data field is empty for that. can anybody help by this, please?

Answer 1

To do this Matlab recommends the Object Save and Load Process. This requires defining two methods for each class, that handle storing the data as a structure and then later re-converting this structure into the class type.

The Mathworks documentation show an example of a basic saveObj & loadObj pattern, with storing the result in a .mat file, before reloading the data back.

You will need to do this for every class you wish to save the properties for.

---

For reference :

classdef GraphExpression
   properties
      FuncHandle
      Range
   end
   methods
      function obj = GraphExpression(fh,rg)
         obj.FuncHandle = fh;
         obj.Range = rg;
         makeGraph(obj)
      end
      function makeGraph(obj)
         rg = obj.Range;
         x = min(rg):max(rg);
         data = obj.FuncHandle(x);
         plot(data)
      end
   end
   methods (Static)
      function obj = loadobj(s)
         if isstruct(s)
            fh = s.FuncHandle;
            rg = s.Range;
            obj = GraphExpression(fh,rg);
         else
            makeGraph(s);
            obj = s;
         end
      end
   end
end

This can be used as :

>>> h = GraphExpression(@(x)x.^4,[1:25])
>>> h = 
>>>
>>>  GraphExpression with properties:
>>>
>>>    FuncHandle: @(x)x.^4
>>>         Range: [1x25 double]

And then stored and re-loaded with :

>>> save myFile h
>>> close
>>> load myFile h