Object Oriented Programming question: creating child objects and sum one property of all children and the parent

Hi,

I'm just getting into matlab OOP and got stuck in creating child ojbects. I have a class like

classdef myClass

  properties
    myVar;
    myNumber;
    myName;
  end
  
  methods
    function m = myClass(name,number,value)
      m.myName = name;
      m.myVar = value;
      m.myNumber = number;
    end
    
    function printTotalValue(name)
      disp(['Total value: ' num2str(name.myVar)]);
    end
  end
end

I can see the "total value" by running the commands

clear classes
a = myClass('apa',1,10);
a.printTotalValue;

I now want to create a hierarchy of objects, and whenever I call object.printTotalValue I want it to sum it's value and the value of all it's children, grand children etc. But how do I do this?

I want to index the hiearchy by myNumber, like this:

ObjNo1     (myName = "object 1"; myVar=3; myNumber=1)
.Obj11     (myName = "object 11"; myVar=1; myNumber=11)
..Obj111     (myName = "object 111"; myVar=30; myNumber=111)
..Obj112     (myName = "object 112"; myVar=15; myNumber=112)
..Obj113     (myName = "object 113"; myVar=2; myNumber=113)
.Obj2     (myName = "object 2"; myVar=1; myNumber=2)
.Obj3     (myName = "object 3"; myVar=23; myNumber=3)
..Obj31     (myName = "object 31"; myVar=6; myNumber=31)

And then I want to be able to call ObjNo113.printTotalValue and get 2 as result, ObjNo11.printTotalValue and get 1+30+15+2=48 as result, ObjNo2.printTotalValue and get 2 as result, etc...

But: *How do I create child objects like this? * *How do I get a list of all child objects and overload the printTotalValue function so it sums all the myVar's for the children objects? *

I've been googling for quite some time but can't seem to find an answer that gets me through this, so any help would be appreciated!

Thanks in advance, Anders

Answer 1

[Malcolm Lidierth]

You could try something like this:

classdef myClass < hgsetget

  properties
        ParentObject=[];
        ChildObjects={};
    myVar;
    myNumber;
    myName;
  end
  
  methods

  function thisObject = myClass(name,number,value)
    thisObject.myName = name;
    thisObject.myVar = value;
    thisObject.myNumber = number;
  end

          function addChild(thisObject, newObject)
              thisObject.ChildObjects{end+1}=newObject;
              newObject.ParentObject=thisObject;
          end

          function object=getChild(thisObject, n)
              object=thisObject.ChildObjects{n};
          end

  end
end

Then at the command line:

>> a=myClass('Eve', 1, 22);
>> a.addChild(myClass('Cain',2,99));
>> a.addChild(myClass('Abel',3,999));
>> a.getChild(1).addChild(myClass('Enoch',4,1999));

printTotalValue can then just search upwards using the ParentObject entry until it finds it empty.

[Anders Österling]

You're a star Malcolm!! Your code saved me hours - I was not even close to inherit from hgsetget before reading it!

I added a method for looping through all the children and then I was done. Here's the final code:

classdef myClass < hgsetget properties ParentObject=[]; ChildObjects={}; myVar; myNumber; myName; childSum; familyValue=0; addedMyVarBool=0; end

methods
  function thisObject = myClass(name,number,value)
    thisObject.myName = name;
    thisObject.myVar = value;
    thisObject.myNumber = number;
  end
  function addChild(thisObject, newObject)
    thisObject.ChildObjects{end+1}=newObject;
    newObject.ParentObject=thisObject;
  end
  function object=getChild(thisObject, n)
    object=thisObject.ChildObjects{n};
  end

    function sumVar=loopThroughOffspring(thisP,sumSoFar)
      %This function loops through all the offspring of an object and
      %returns the myVar for each object.
      noChildren = length(thisP.ChildObjects);

      %update the sum with the value for this object
      sumVar = thisP.myVar + sumSoFar;

      %also go through all children of this object:
      if noChildren >0
        for i=1:noChildren
          sumVar = loopThroughOffspring(thisP.getChild(i),sumVar);
        end
      end
    end
  end
end

in command window i run:

    clear classes
    a=myClass('Object 1', 1, 3);
    a.addChild(myClass('Object 11',11,1));
    a.getChild(1).addChild(myClass('Object 111',111,30));
    a.getChild(1).addChild(myClass('Object 112',112,15));
    a.getChild(1).addChild(myClass('Object 113',113,2));
    a.addChild(myClass('Object 12',12,3));

    sumVar = a.loopThroughOffspring(0)

and it returns 54 - the sum of all the .myVar.