Create an array of distinct objects of handle class

Question

Michael 2024-4-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2109061-create-an-array-of-distinct-objects-of-handle-class

编辑： Bruno Luong 2024-4-19

采纳的回答： Bruno Luong

I want to store objects of a handle class in an array.

When using

for i=1:2

arr(i) = uilabel;

end

arrFor(1).Text = "textFor 1";

arr(2).Text = "textFor 2";

the objects in the array are distinct.

When using

arrDir(1:2) = uilabel;

arrDir(1).Text = "textDir 1";

arrDir(2).Text = "textDir 2";

both text will change to "textDir 2" which makes sense because uilabel is a handle class.

What is the syntax to avoid the for loop and diretly crating an array of distinct objects of a handle class?

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Steven Lord 2024-4-19

Why is the for loop not a desirable solution for you?

Michael 2024-4-19

Because it is bulky, clutters the code and not very efficient.

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Answer 1

Bruno Luong 2024-4-19

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https://ww2.mathworks.cn/matlabcentral/answers/2109061-create-an-array-of-distinct-objects-of-handle-class#answer_1444496

编辑：Bruno Luong 2024-4-19

在 MATLAB Online 中打开

Why not simply calling the constructor as many time as you need

arrDir = arrayfun(@(~)uilabel, 1:2);
arrDir(1).Text = "textDir 1";
arrDir(2).Text = "textDir 2";
arrDir(1).Text

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Bruno Luong 2024-4-19

You could probably declare a subclass and over load the subsref subsasg methods and erase the handle copy behavior.

First of all I never did such thing. Second: it is just adding layer on layer and tweak the initial design pattern. It become dirty diffuclt to maibtain understand the code.

Michael 2024-4-19

Under the hood this is basically the same thing as the for loop with the drawback of more difficult debugging but more compact code. Regarding the other answers this seem to be the best option. Thank you.

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Answer 2

Fangjun Jiang 2024-4-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2109061-create-an-array-of-distinct-objects-of-handle-class#answer_1444521

As long as uilable() can only create a single object, there is no way to avoid the loop.

In arrDir(1:2) = uilabel, the same single handle was assigned to the two elements of arrDir.

What you should look for, is whatever the object class that you are working on, whether its creation method has the capability or syntax to create multiple objects in one shot.

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Michael 2024-4-19

编辑：Michael 2024-4-19

This answers the question. It is not what I hoped but in that case arrayfun seems to be the cleanest way to handle this case.

Do you know why there is no such functionality? Seems like there might be plenty of usecases where this could be really helpful, especially when dealing with user interfaces.

Is there some underlying Matlab voodoo why this does not male sense?

Bruno Luong 2024-4-19

编辑：Bruno Luong 2024-4-19

Well a lot pf people use object (graphical) handles for decades, I don't see that often the need of deep copying handls or clonig them to an array.

If they do often the constructor is invoked as many as it needs, whereas it is manually unroll out, inside a for-loop or wrapped into an arrayfun/cellfun.

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