[asterisk-users] AEL: how to check if variable is defined

[Philipp Kempgen]

Klaus Darilion schrieb:
> I use an "if" condition in extensions.ael to check if a channel variable 
> is defined and if defined I add a certain header:
> 
> context toNormaleRufe {
>    _X. => {
>             if (${NUMBER}) {
>                 SIPAddHeader(X-NUMBER: ${NUMBER});
>             };
>             ...
>    };
> 
> This works fine, except NUMBER starts with the + sign.
> 
> I tried using quotes but
>     if ("${NUMBER}")
> evaluates always true.
> 
> What is the suggested way to solve this?

if ("${NUMBER}" != "") {
    // ...
}

That doesn't tell you whether the variable is defined but in
most cases (if any) that doesn't matter anyway.

   Philipp Kempgen

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