Check if a function handle is valid
显示 更早的评论
I use str2fun(...) to create a function handle from a user-inputted string. I want to be able to run a check to make sure the function created is valid and no typos were made. I could not find a way to do this. Any suggestions?
Thanks, Ryan
MATLAB R2014a
1 个评论
Steven Lord
2021-2-26
What is a "valid" function handle?
f = @quit; % NOTE: Don't execute f if you have data in your MATLAB session you need!
f is a "valid" function handle in that it won't error when called. But you may not want users to enter 'quit' as the user-inputted string and blindly evaluate that function handle -- the "Bobby Tables" scenario.
g = @() zeros(1:12); % MAY error or MAY succeed and take a LONG time doing so
This may successfully execute (though it may take a while) or may throw an error depending on your computer's memory availability and your MATLAB settings. Is it "valid"?
采纳的回答
Kurt Schmutz
2014-9-18
Hi Ryan
To CHECK whether a function handle is valid or not (without trial-and-error) you can do the following:
f = str2func('nameofthefunction')
fh = functions(f)
if isempty(fh.file)
% invalid :(
else
% valid :)
end
Note: file "nameofthefunction.m" must be in the current folder
Cheers, Kurt
MATLAB R2013b
4 个评论
Sean de Wolski
2014-9-19
This could fail if the function is an anonymous function which doesn't have a file.
x = @(x)x^2;
Kurt Schmutz
2014-9-22
Hi Sean,
obviously it will fail in this case!
Thanks for the hint :)
Ryan
2014-9-22
David Sinex
2021-2-26
This fails if the function is a class member.
更多回答（3 个）
Sean de Wolski
2014-7-1
try
fun()
catch
disp 'didn''t work'
end
Try it and catch failures. Or provide a listbox with known functions to remove the human typing element.
Ryan
2014-7-1
0 个投票
1 个评论
Sean de Wolski
2014-7-1
Well if you catch the MException, you could look at the message of it.
...
catch ME
ME.message
end
Jos (10584)
2014-9-19
0 个投票
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