Get pointer of class object - matlab

Question

I have an object apple created by my own class in MATLAB:
apple = classA();
The class looks like this:
classdef classA < handle
properties
color = 'red';
end
methods
function obj = classA()
% ...
end
end
end
The question: How do I get the object or handle pointer of apple? I want to search for objects by their properties, like:
isprop(eval(mat(i).name),'color')
with mat = whos. So I need to get the pointer of the object, represented by the struct mat(i).name. I just need the reference, not a copy of the desired object. The purpose is this:
If I get the pointer somehow, like
ptr_to_apple_object = get_pointer_fct( mat(i).name )
then I am able to change the properties of the apple-object like:
ptr_to_apple_object. color = 'yellow'
Do you have any ideas? Thanks.

Answer 1

There's really no good way to find all current objects of a particular class, but you could use whos to get a struct about all variables, loop through this and determine which ones have the property you and then modify
variables = whos;
for k = 1:numel(variables)
obj = eval(variables(k).name);
if isobject(obj) && isprop(obj, 'color')
obj.color = 'yellow';
end
end
If you're looking for a specific class, you can use the class field of the output of whos
is_class = ismember({variables.class}, 'classA');
instances = variables(is_class);
for k = 1:numel(instances)
obj = eval(instances(k).name);
obj.color = 'yellow';
end
Update
Since you are subclassing handle, when you assign your instance to a new variable (obj = val(variables(k).name) above), it does not create a copy of your instance, but rather a new reference to the same object.
b = classA;
c = b;
b.color = 'red';
c.color
% 'red'