MATLAB: Passing options from subclass constructor to superclass

classfunctionMATLAB

I really like the new "arguments" way to pass values, including optional values. However, one really nice feature of the (old?) varargin approach was that you could just pass the whole thing along. But with arguments, if I have a subclass that only needs a couple options and is happy to pass the rest to its superclass, I don't see a great way to do that. I've found that I need to specifically implement every option and pass them specifically. I'm probably missing something, but would love to learn what. Thanks! — David

Best Answer

Can't you just convert the options structure back to a cell array of name value pairs and use that to call the super class constructor? Using the attached function struct2pairs, this would be

       function ourPicture = TakePicture(obj, aCIScene, intent, options)
           
           arguments
               obj;
               aCIScene;
               intent;
               options.numHDRFrames = 3;
               options.numBurstFrames = 3;
               options.imageName char = '';
               options.reRender (1,1) {islogical} = true;
           end
...        
          varargin=struct2pairs(options);
          ourPicture = TakePicture@ciCamera(obj, aCIScene, intent, varargin{:});;        
       end

Related Solutions

MATLAB: Passing arguments to varargin

Picking up from your idea you should just be able to use

varargin{:}

inside your function after passing in options rather than passing in options{:} to achieve the same effect.

Personally I tend to do this kind of thing using object-oriented programming, but that is just preference as I do most of my Matlab programming OOP now, so just throwing it out there as an alternative that you might find neater or are free to completely ignore :)

e.g. I have loads of what I call Args classes which are simple classes with all public properties, just like a struct really, but properly defined.

As an example (bear in mind I have just typed this straight off the top of my head not in Matlab so apologies if it contains syntax errors, it is mostly to put the idea across).

classdef MyFuncArgs
     properties( Access = public )
         % All your arguments here with their default values
         varA = 7;
         varB = [15 20 23];
     end
     methods
         function obj = set.varA( obj, varA )
             validateattributes( varA, { 'numeric' }, { 'scalar', 'positive' } );
             obj.varA = varA;
         end
         function obj = set.varB( obj, varB )
             validateattributes( varA, { 'double' }, { 'vector', 'numel', 3, '>' 5, '<=' 25' } );
             obj.varB = varB;
         end
     end
  end

then my function can just take an object of that class as input, I can do a single validateattributes on it to check it is an object of type MyFuncArgs and all the validation of the parameters was done by the Args class so I know in my function that they are there ready for use.

The default values are programmed into the Args class as shown above in the example so that you can either just pass in a default Args class (or create one inside your function if Args is an optional argument to the function) or you can change only as many parameters as you want from defaults and the Args class set functions will ensure you can only set valid parameters.

Where possible I like to set up these Args classes so that the default values are what I most commonly use. So I have a PlotArgs which I use for a Plotter class I have which sets a colourmap, does interpolation, etc, etc in the manner I usually want it, but I can switch off interpolation, change colourmap, etc in that PlotArgs object.

So for example.

args = MyFuncArgs;
args.varB = [10, 12, 13];
y = my_fun( a, b, args );

MATLAB: How extract data from image saved in fig format

fig = openfig('FigFileName.fig', 'new', 'invisible');
imgs = findobj(fig, '-type', 'image');
thiscmap = get(fig, 'colormap');
for K = 1 : length(imgs)
  thisimg = get(imgs(K), 'CData');
    %now do something with it for illustration purposes
    thisfilename = sprintf('extracted_image_%03d.jpg', K);
    imwrite(thisimg, thiscmap, thisfilename);
  end

Best Answer

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MATLAB: Passing arguments to varargin

MATLAB: How extract data from image saved in fig format

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