Validating/identifying an "undefined" array element

programming flash
1

I’m passing an array as an argument to a class, like this:

 
formatArray = [string, number, number,
               string, number, number,
               string, number, number,
               string, number, number,
               string, number, number];

The class, which converts the array to _formatMatrix, is is set up to EXPECT the array to contain 15 elements. In the class, I do this:


switch (_formatMatrix[12]) {
     // do something
}

When I pass formatArray containing only four sets of <string, number, number> rather than five, I get this error:


Error #2007: Parameter format must be non-null.

I have tried adding a conditional to the class that makes it disregard the fifth set thus:


if (_formatMatrix[12] = null) {
    trace("_formatMatrix[12] is undefined!");
} else {
    // do something
}

This doesn’t work – I still get the 2007 error, and I don’t see the trace. Meaning, I never get to the conditional because Flash doesn’t like that I have not included the fifth set. I have also tried…


if (_formatMatrix[12] = undefined)

…but that doesn’t work and I don’t actually know if that’s valid.

What do I need to do to make the class allow me to pass an “incomplete” array?

Thanks!