pointers in object-oriented matlab programing

I want to create several objects that can "communicate with each other"

for instance, let's say i have a class called "child" and a class called "woman", and i want each child to have a property "mother" and each woman to have a property "children". these properties should contain some sort of pointer to the other objects, so that i can (for instance) add a function to the "woman" class named "feed_children" and i can go over all all her children and change some parameter.

is there a way to do this? i note here that i don't want to simply use some sort of structure, where the children are contained in a "struct" inside the "mother" object. i want all the objects to appear in the workspace and have independent existence, but to have some way of pointing at each other. i know that in many object oriented languages this is very easy to do

many thanks

i attach here my code if anyone is interested, the "TA_system" class is the mother (components are children) and a duct is a component.

[Walter Roberson]

MATLAB objects derived from "handle" class effectively use pointers.

[nathan blanc]

thank you for your answer walter, could you expand on that? i tried to read about handle objects before posting the question, my understanding was that they cannot do what i am tryind to do. could you explain how you would do what i asked uding handle objects?

Answer 1

[Walter Roberson]

classdef woman < handle
    properties
        children = handle([]);
    end
    methods 
        function obj = woman
        end
        function addchild(obj, this_child)
            obj.children(end+1) = this_child;
        end
    end
end

classdef child < handle
    properties
        mother = handle([]);
    end
    methods
        function obj = child(this_mother)
            obj.mother = this_mother;
            addchild(this_mother, obj);
        end
    end
end

[Steven Lord]

You need to make the mother and children properties arrays of the correct type. I'd use the empty method.

children = child.empty(1, 0);

mother = woman.empty(1, 0);

Also addchild() probably also needs to update the child's mother property.

% Two women
>> w1 = woman;
>> w2 = woman;

% Two children, one for each mother
>> c1 = child(w1);
>> c2 = child(w2);

% Woman w1 now has two children, c1 and c2.
>> addchild(w1, c2);
>> numel(w1.children)
ans =
     2

% But woman w1 is not child c2's mother     
>> isequal(c2.mother, w1)
ans =
  logical
   0

% Woman w2 is still child c2's mother
>> isequal(c2.mother, w2)
ans =
  logical
   1

Either c2's mother property should change to list only w1 as c2's mother or it should change to list both w1 and w2 as c2's mother. In the latter case you probably also need a way to remove a child or mother from the appropriate property.

[Walter Roberson]

In the interface I tossed together, addchild should probably be a private method with access granted specifically to child. You would never call it directly: when you call child() you have to pass in the mother information and the constructor for child invokes addchild on the mother.

You would certainly want to improve the interface: adoption, surrogate mothers, same-sex marriage, blended eggs, children of unknown mothers...

[Steven Lord]

All that is true, and those are good points for nathan blanc to consider when designing their real class hierarchy. Sometimes the process of designing a class hierarchy can be more difficult and/or time consuming than implementing it!

[nathan blanc]

thank both of you

[Walter Roberson]

Yes, figuring out what actually want to do can be tough! And knowing when to stop designing can be hard!

Answer 2

[James Tursa]

MATLAB does not have variable pointers ... at least not in the sense of C/C++ like you are probably alluding to.

[nathan blanc]

how a about a different sense? is there a way to do what i am trying to do?