How can I bypass the property SET methods when loading a MATLAB class object from a MAT-file in MATLAB 7.6 (R2008a)?

While loading MATLAB class objects from a MAT-file, the LOAD function invokes the SET methods of the individual properties to reconstruct the objects. In my code, this procedure may lead to undesirable results: certain SET methods modify the values of multiple properties. Because the order in which the SET methods are invoked cannot be determined beforehand, I receive objects that are not reconstructed in the way I had saved them. Below is an example class:

classdef polygon

     properties

Vertices = zeros(0,2);

     NumPoints = 0;

end

    methods

         function Obj = set.NumPoints(Obj,n)

                  Obj.NumPoints = n;

Obj.Vertices = zeros(n,2);

        end

    end

end

If I execute the following code at the MATLAB command prompt:

p=polygon;

p.NumPoints=4;

p.Vertices=[-1 -1; 1 -1; 1 1; -1 1];

save test.mat

clear

load test.mat

p.Vertices

I will receive the following output:

 ans =

      0     0

      0     0

      0     0

      0     0

when I expected p.Vertices to remain a matrix of 1's and -1's.

Answer 1

[MathWorks Support Team]

The ability to bypass the SET and GET methods when loading an instance of a MATLAB class is not available in MATLAB.

A possible workaround is to overload the SAVEOBJ function to save the object's properties into a struct that in turn can be saved into a MAT-file. The LOADOBJ should also be overloaded to execute the SET methods in the appropriate order when reconstructing the object. The code for the above described functions can be found below:

function s = saveobj(obj)

    % save properties into a struct.

    % Pass that struct onto the SAVE command.

     s.NumPoints = obj.NumPoints;

     s.Vertices = obj.Vertices;

end

function obj = loadobj(s)

    obj = polygon;

    obj.NumPoints = s.NumPoints;

    obj.Vertices = s.Vertices;

end

Note that LOADOBJ must be a static method. A class file incorporating the above two functions can be found attached.