passing handle objects by value

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mahdi Babayi semiromi 2021-7-13

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https://ww2.mathworks.cn/matlabcentral/answers/877613-passing-handle-objects-by-value

评论： Yongjian Feng 2021-7-13

Hi

I have a class inheriting from the "handle" class, which means (correct me if I'm wrong) it will have reference semantics. I use an instance of the class in a simulation loop and I'd like to save a sanpshot of the object in every iteration. Is there a way to dereference the handle object and pass it by value to store it in a cell array?

Thanks for your replies in advance

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Answer 1

Steven Lord 2021-7-13

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Have your class inherit from matlab.mixin.Copyable as described on this documentation page.

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mahdi Babayi semiromi 2021-7-13

Thanks

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Answer 2

Yongjian Feng 2021-7-13

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You don't need to.

classdef aclass < handle
    properties
        a
    end
end
l={}
a = aclass();
a.a = 10;
l{end+1} = a;
a = aclass();
a.a = 20;
l{end+1} = a;
l{1}
l{2}

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mahdi Babayi semiromi 2021-7-13

编辑：mahdi Babayi semiromi 2021-7-13

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Thank you very much for your reply

This is different from the application that I have in mind. my case is like the following:

classdef aClass < handle 
    properties 
        a
    end
end
aClassInstance = aClass;
l = {};
for i = 1:2
    aClassInstance.a = i;
    % here I want to save the variable aClassInstance by value, so that I
    % have it in its current state. If I just assign it to a cell array,
    % like:
    l{end+1} = aClassInstance;
    % then l{end+1} will only hold a pointer to the variable aClassInstance
    % and when I exit the loop, I'll only have access to the latest state
    % of the variable 
end

Yongjian Feng 2021-7-13

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Can you just move the initialization line inside the for loop?

classdef aClass < handle 
    properties 
        a
    end
end
l = {};
for i = 1:2
    aClassInstance = aClass;
    aClassInstance.a = i;
    % here I want to save the variable aClassInstance by value, so that I
    % have it in its current state. If I just assign it to a cell array,
    % like:
    l{end+1} = aClassInstance;
    % then l{end+1} will only hold a pointer to the variable aClassInstance
    % and when I exit the loop, I'll only have access to the latest state
    % of the variable 
end