Bug: class field modified by reference

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Antonio Mei
Antonio Mei 2018-6-1
评论： Antonio Mei 2018-6-1
There is a major bug in Matlab in which the field of a class is modified when passed as an function argument but not requested as an output if the calling function modifies the value internally. In the minimal example below: b.value is not the same before and after calling test.
b.value = 10;
b.value,
a = test(b);
b.value
function a = test(b)
a=1; b=b.value*10;
end
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Antonio Mei
Antonio Mei 2018-6-1
Right, it only happens for when b is defined via classdef.
Walter Roberson
Walter Roberson 2018-6-1
Please post actual example including classdef

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Steven Lord
Steven Lord 2018-6-1
I tried this with a very simple class and it worked as I expected.
It sounds to me like b is an instance of a handle class. If that's the case, the behavior you described is correct as described in the "Handle Objects Modified in Functions" section on that documentation page (assuming that in your test function you assigned into the value property of the b object rather than overwriting the variable inside the function.) See the attached example. I expect the last line printed when you run that code to be "ans = 100".
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Antonio Mei
Antonio Mei 2018-6-1
Thank you for clarifying. I actually had used the "dynamicprops" property. Do you know of a way to dynamically define properties without recursing to a handle subclass?

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