Multiple Outputs in object method?

I'm working with OOP in matlab and I want to define a function to output multiple arguments. The idea is to easily concatenate the output or put in a cell array depending on my usage.

function varargout = getPoints(self)
    if numel(self) > 1
        for i = 1:numel(self)
            varargout{i} = self(i).getPoints;
        end
    else
        %Computation to get the points, results is always a 2x2 matrix
    end
end

The idea now is now in other objects I can easily manipulate the results like

 a = cat(3, allObjects.getPoints);

or like this

 b = {allObjects.getPoints};

But I always just get one output out, only the first entry. How can I achieve the desired effect? Thanks in advance!

Answer 1

[Guillaume]

The problem is that when you do

cat(3, allObjects.getPoints)
%or
{allObjects.getPoints}

you're only asking for one output. So, only the first cell of varargout is going to be used.

You could work around this, by assigning the output of your getPoints function to a cell array of the right size, like so:

c  = cell(1, numel(allObjects)); 
[c{:}] = allObjects.GetPoints;
cat(3, c{:})

The other option is to change GetPoints to always have a single output:

function points = GetPoints(self)
   %points is a cell array if self is an array, a matrix otherwise
   if numel(self)
      points = arrayfun(@(s) s.GetPoints, self, 'UniformOutput', false);
      %or use your loop
   else
     %computation
   end
end

In which case, the code on the receiving side is simply:

points = allObjects.GetPoints;
cat(3, points{:})

[David]

So there is no way to "force" more outputs like what happens when you index into cell array?

a = cell(10,1)
a{:} % This results in multiple outputs

[Guillaume]

Not as a far as I know.

Another option is to use a property instead of a method. Then you could do:

cat(3, allObject.Points)

You could even make that Points property a dependent property, so that the points are calculated on the fly as you do in your GetPoints method:

classdef SomePointClass
   properties (dependent)
      Points;
   end
   methods
      function points = get.Points(self)
         %self is always scalar. If property is requested for an array
         %matlab passes the array elements one by one to this function
         %so always do points computation here as in the else clause
         %of your GetPoints
         points = randi(100, 5, 4); %e.g.
      end
   end
end

[David]

Yes I know that, but that means I cannot pass additional options and overloading in child classes gets cumbersome. Thanks for the help!