How can I use dynamic field names instead of setfield inside a function call?
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In the following call, I have an existing structure Syst0. I want to call a function with as an argument Syst0 with a field set to a value:
HwErr1 = TracePeriodicSys(setfield(Syst0,'AngleError',Err1));
This line generates a yellow caution triangle with the note "Use dynamic fieldnames with structures instead of SETFIELD". How do I do this without creating a temporary structure (e.g.,
SystTemp=Syst0;SystTemp.AngleError=Err1;HwErr1 = TracePeriodicSys(SystTemp);
I think maybe this caution is erroneous.
4 Comments
Walter Roberson
on 17 Oct 2019
The side effect is in the temporary variable that MATLAB creates.
Your code is equivalent to
HwErr1 = TracePeriodicSys(subsasgn(Syst0, struct('type', '.', 'subs' {'AngleError'}), Err1));
This does not modify Syst0: it creates a temporary variable to do the assignment into, and passes the result as output.
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