Question

I’m a little bit new to Actionscript, but I can’t figure this one out. I’ve done a lot of searching on this topic and haven’t found a clear answer. I’ve tried the following solutions that people posted online but none of them work.

All the following solutions give the error: 1120: Access of undefined property myVariable

Suggestion #1:

try {
     trace(myVariable); }
catch {
     trace("your variable doesn't exist"); }

Suggestion #2:

if (myVariable) {
     trace("your variable exists!!"); }
else {
     trace("it doesn't exist"); }

Suggestion #3:

if ( myVariable == null )
     trace("your variable doesn't exist");

Suggestion #4:

if ( myVariable == undefined )
     trace("your variable doesn't exist");

Like I said, I’ve found many forums posts and stuff online that give the above suggestions saying they will work, but they all seem to be giving me that same 1120: Access of undefined property myVariable error.

By the way, in case you are wondering why I would need to check if a variable exists or not, I’m planning on passing variables to the SWF in its URL, so I need to make sure the proper variables exist and handle the code properly if they are not passed in.

---

Thanks for the quick reply. Still not really working. The scope of the variable is just on the top/root level of the script. Basically, I start a new flash file, on the first frame I add the following action:

// to check for this.myVariable
if ( this.hasOwnProperty( "myVariable" ) ) {
     trace("myVariable exists");
}
else
{
     //Variable doesn't exist, so declare it now
     trace("declaring variable now...");
     var myVariable = "Default Value";
}

trace(myVariable);

When I run the flash file, I get this output:

myVariable exists
undefined

I was expecting this:

declaring variable now...
Default Value

Answer 1

By the way, in case you are wondering
why I would need to check if a
variable exists or not, I’m planning
on passing variables to the SWF in its
URL, so I need to make sure the proper
variables exist and handle the code
properly if they are not passed in.

Then you are taking the wrong approach. Here’s the right way™ to read and validate SWF parameters, along with default value if they don’t exist:

private function parameter(name:String, defaultValue:String):String
{
        // Get parameter list
    var paramObj:Object = LoaderInfo(stage.loaderInfo).parameters;

        // Check if parameter exists
    if(paramObj.hasOwnProperty(name) && paramObj[name] != "")
        return paramObj[name];                     
    else
        return defaultValue;
}

Warning! Since this relays on the ‘stage’ property, Use this code either from the Document Class or after Event.ADDED_TO_STAGE.