How can I make an object declared within a function persistent?

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Warren Koontz 2015-6-16

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https://ww2.mathworks.cn/matlabcentral/answers/224093-how-can-i-make-an-object-declared-within-a-function-persistent

评论： Warren Koontz 2015-6-17

I have defined two handle classes for audio filters (LPcomb and APfilt). I would like to write a function to apply these filters to streaming audio on a block-by-block basis. So I declare the object variables to be persistent. In the "if isempty - end" block I try to instantiate these variables as objects of my classes. I get the following error message:

The following error occurred
converting from LPcomb to double:
Error using double
Conversion to double from LPcomb
is not possible.

So it seems that when you declare a variable to be persistent, it is declared as a double and cannot be instantiated as an object. How can I declare persistent objects in a function?

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Guillaume 2015-6-16

I cannot reproduce the problem. Can you post the code that is creating the error?

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Answer 1

Eric Lin 2015-6-17

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https://ww2.mathworks.cn/matlabcentral/answers/224093-how-can-i-make-an-object-declared-within-a-function-persistent#answer_183015

As Guillaume notes, we'll need the code in question to help you further.

However, it is important to note that persistent variables are initialized as double arrays so a type change must first be performed if you would like the persistent variable to store non-double elements, as discussed in this answer: Trouble with persistent array of class objects

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Warren Koontz 2015-6-17

在 MATLAB Online 中打开

Thanks. The information in the link you provided fixed the problem. Here is a partial listing of the "before" code:

    comb(Nc)=LPcomb;
    for n=1:Ncf
        comb(n)=LPcomb(cfDelay(n),damp,fbck);
    end

Here is the same code "after"

    comb=LPcomb;
    for n=1:Ncf
        comb(n)=LPcomb(cfDelay(n),damp,fbck);
    end

In both cases, comb and Nc are persistent. No error message for the "after" version and the function worked fine. I didn't even get the warning about dynamic allocation!

Thanks for your help.

PS - This OO version ran MUCH more slowly than its non-OO predecessor!

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