Stumped trying to implement Save/Load object functionality in a MATLAB UI

Answer 1

Don't assign values to self. All that does is replace the binding to the self variable in the scope of the method call. It does not call a magical copy constructor to replace the object reference in the caller. Instead, copy the fields into self. Try something like:

if isfield(tmp,'obj')
   self.image = tmp.obj.image;
   self.objCount = tmp.obj.objCount;
end

Answer 2

I believe Mr Fooz is right. The self variable passed to load_object is an object of type "myObj", but the line:

self = tmp.obj;

is simply overwriting the self variable with the structure stored in tmp.obj. Doing:

self.image = tmp.obj.image;

should instead invoke a set operator for the image property of object self. In the MATLAB documentation there is a sample class definition with a method called "set.OfficeNumber" that illustrates this.

In addition, the following line in your function savingMyObject may be unnecessary:

obj = self;

I think it might make most sense (and make the code a little clearer) if you used the name "obj" in place of the word "self" within your class code (as the documentation tends to do). "self" doesn't appear to be any kind of special keyword in MATLAB (like it may be in other languages). It's just another variable as far as I can tell. =)

EDIT #1:

If the prospect of having to set each property individually in your load_object method doesn't sound like fun, one way around it is if you have a SET method for your object that is designed like the SET method for handle graphics. That SET command can accept a structure input where each field name is a property name and each field value is the new value for that property. Then you would have one call like:

set(self,tmp.obj);

Quite a bit shorter, especially if you have lots of properties to set. Of course, you'd then have to write the new SET method for your object, but the shortened syntax may be worth the extra work if it comes in handy elsewhere too. =)

EDIT #2:

You may be able to use the loop Mr Fooz suggested in conjunction with a try/catch block:

fn = fieldnames(tmp.obj);
for i = 1:numel(fn),
  try
    self.(fn{i}) = tmp.obj.(fn{i});
  catch
    % Throw a warning here, or potentially just do nothing.
  end
end

Answer 3

Combining Mr Fooz's and gnovice's suggestions, I added a SET function with the following definition

function set(self,varargin)
    if isa(varargin{1},'FujiCalibration')
        tmp = varargin{1};
        fns = fieldnames(self);
        for i = 1:length(fns)
            if strcmpi(fns{i}(1:2),'p_')
                self.(fns{i}) = tmp.(fns{i});
            end
        end
        self.calibImage = tmp.calibImage;
    else
        proplist=fields(self);
        for n=1:2:length(varargin)
            tmp = proplist(strcmpi(proplist,varargin{n}));
            value = varargin{n+1};
            switch length(tmp)
                case 0
                    msg = char(strcat('There is no ''', varargin{n}, '''property'));
                    error('FujiCalibration:setPropertyChk',msg)
                case 1
                    tmp = char(tmp);
                    self.(tmp) = value;
            end
        end  
    end
end

I then modified the load_object method as suggested by gnovice by changing

self = tmp.obj

to

set(self,tmp.obj).

I need to make sure that properties with values I want to persist are prefixed with 'p_'.

Thanks to gnovice and Mr Fooz for their answers.