Is it possible to tell if another set method call is coming up?

I have an object that does a somewhat long calculation, stores the result, and then lets the user use it. If they change certain properties then it needs to be recalculated. So, in the set method for those properties, I just call the precalculation method. Ideally, if the user changed multiple properties at the same time - for example, set(obj,'A',a,'B',b) - then it wouldn't do the calculation twice. Is it possible for me to check how the set method was called? Ideally I could write something like:

 classdef foo < matlab.mixin.SetGet

 properties (SetAccess=private)
    Expensive=[];
 end

 properties
    a=1;
    b=2;
 end

 methods
      function DoSomethingHard(obj)
         Expensive=SomeLongCalculation(obj.a,obj.b);
      end

      function set.a(obj,value)
         obj.a=value;
         if NoMoreSetCallsComingUp
            obj.DoSomethingHard;
         end
      end

      function set.b(obj,value)
         obj.b=value;
         if NoMoreSetCallsComingUp
            obj.DoSomethingHard;
         end
      end

 end
 end

Except I don't know what "NoMoreSetCallsComingUp" would look like. Is this possible? Currently I'm just doing a lot of unnecessary computations...

[Greg]

If my recommended answer doesn't work, you might be able to do evalin('caller','nargin') to determine if multiple set commands were issued.

This is a VERY bad idea, for various reasons. Use at your own risk.

Answer 1

[Greg]

I can't test it on this machine to confirm, but you should be able to define set for your class (as opposed to set.a and set.b individually). Then, parse the parameter-value pairs and call doSomethingHard at the end.

methods
    function DoSomethingHard(obj)
       Expensive=SomeLongCalculation(obj.a,obj.b);
    end
    function set(obj,varargin)
       % Obviously want better input checking...
       for iarg = 1:2:length(varargin)
         obj.(varargin{iarg}) = varargin{iarg+1};
       end
       % Best practice is to call methods method(obj) vs. obj.method
       % avoids confusion between methods and properties 
       DoSomethingHard(obj);
    end
end