Voxeo Developers Corner

Here in Support we get a fair amount of tickets asking about variables.  Namely, if a variable is created in a form can it be accessed in the field of that form or in a different form? What I am talking about is called variable scoping.  In VXML there are several different variable scopes.  You might have heard of global and local variables with other programming languages.  VXML, while not a programming language, is similar in how it approaches variables and how they can be accessed.

First lets get a proper definition for variable scope.  The scope of a variable defines when and where the variable exists and may be accessed. When the VXML browser exits the scope where the variable is defined, the variable is out-of-scope and cannot be accessed. When a variable is in scope, it can be accessed by both VoiceXML and ECMAScript.

Here is a table of the different scope levels of variables in VXML:

Here is an example of document scoped variable.  As you can see it is accessible throughout the current VXML document.

<?xml version=”1.0″?> <vxml version=”2.0″>

<var name = “counter” expr = “0″/>

<form id=”F_1″> <!– additional VXML code –> <filled> <assign name=”counter” expr = “counter + 1″/> </filled> </form>

<form id=”F_2″> <!– additional VXML code –> <filled> <assign name=”counter” expr = “counter + 2″/> </filled> </form>

</vxml>

Here is an example of a dialog scoped document.  In form “F_1″ the value of “counter” after the assign <element> would be 1.  In form “F_2″ the value after the <assign> value would be 2.

<?xml version=”1.0″?> <vxml version=”2.0″>

<form id=”F_1″> <!– additional VXML code –> <filled> <var name = “counter” expr = “0″/> <assign name=”counter” expr = “counter + 1″/> </filled> </form>

<form id=”F_2″> <!– additional VXML code –> <filled> <var name = “counter” expr = “0″/> <assign name=”counter” expr = “counter + 2″/> </filled> </form>

</vxml>

It is also good to know that variable references will match the closest applicable scope. You can prefix a reference with a scope name, such as application.counter, for clarity or to resolve ambiguity.

We hope this clears up a little confusion about VXML variables and where they are defined and when they can accessed.

Jeremy Richmond VXML Certified Developer

Related posts:

1. Accessing Web Services From VoiceXML
2. VoiceXML for web developers: Hello World
3. Code Walk: Listening to Identi.ca (OSCON 2008 Demo #2: VoiceXML)
4. Demystifying VoiceXML Subdialogs
5. Certified Tech Tip: Alpha-Numeric voice recognition grammars – part two

Tags: Tutorials, VoiceXML

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