MATLAB: Updating property of an Object without creating new object

handleobjectoopupdating methodvalue

Hi
I’m writing a class for the first time, and got an issue I don’t understand.
To simplify the problem, assume my class is as follows:
    ========================================
    classdef testClass
        properties
            count
        end
        methods
            function obj = testClass
                obj.count = 1;
            end
            function obj = increment(obj)
                obj.count = obj.count + 1;
            end
        end
    end
    ========================================
    >> x = testClass;
This creates the class and sets x.count to 1 as required
I then want to increment the value of x.count I was hoping that:
    >> x.increment;
would add 1 to count. But it simply creates a new object (‘ans’), where ans.count == 2
I can of course write,
    >> x = x.increment;
But that feels illogical.
I've tried various things, and Googled the type of problem, but have found a solution. So any guidance would be welcome.
Thanks.  Martyn

Best Answer

When you create a class in MATLAB, it is by default a value class. If you want to update objects by reference, you should make this a handle class by changing the first line to:
classdef testClass < handle
EDIT: Also, you wouldn't necessarily need output arguments for the methods of the handle class.
Check out this documentation page for the differences between value classes and handle classes.
- Sebastian
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