How to check the existence of a non-existent handle

Hello everyone,

is there any way to check if a handle exists or not? So something like: if I didnt previously declare a handle, I want a 0 as output and else a 1.

I tried ishandle,isvalid,isfield,isempty but they all don't work on a "non-existent field" so I receive an error if I didnt declare the handle.. "Reference to non-existent field 'SP'."

If I try the "exist name" function it just works for variables but not for handles

So:

handle.a=figure;
exist handle.a;

returns a 0 (dont know why since the next codepart is working so handle.a strictly speaking has to exist)

while

handle.a=figure;
a=handle.a;
exist a

returns a 1

but I'm looking for something like:

handle.a=figure;
exist handle.a

ans=1

%without setting the handle:
exist handle.a

ans=0

I hope my post is understandable. Thank you for your help! Klaus

Answer 1

[Titus Edelhofer]

Hi Klaus,

I guess

isfield(handle, 'a') && ishandle(handle.a)

is what you are looking for ...?

Titus

[klaus ebert]

Perfect, thank you! This gives me one short other questions, is it possible to convert a string to something which I can use in a function? (so to remove the '' which declare it as a string)

[Titus Edelhofer]

Your welcome... Sorry, but I don't understand the question?

[Walter Roberson]

eval() or str2fun() or matlabFunction() perhaps?

[klaus ebert]

eval() is what I was looking for. Thank you both alot!

[Chandan Prakash]

Thank you...!!