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

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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?

Accepted Answer

Eric Lin
Eric Lin on 17 Jun 2015
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
  1 Comment
Warren Koontz
Warren Koontz on 17 Jun 2015
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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