Actionscript - Obtain the name of the current function

Question

I want to get the name of a function from inside that function. e.g.:

function blah() {
    //I want to get the string "blah" here, from the function's name
}

Or at least the Function object?

Answer 1

Use arguments.callee to get a reference to the current function.

I you want to get the function name, it is a bit trickier: All functions are treated as method closures (pieces of code which can be passed around as an argument), so they do not own a reference to an enclosing class type, nor do they have a "current name".

However, if (and only if) the method is public, and you want to get the method name from the class declaration of an instance object containing the method, you can use describeType:

public function someFunction() : void {
    var callee:Function = arguments.callee;
    trace (getFunctionName(callee, this)); // ==> someFunction
}

private function someOtherFunction() : void {
    var callee:Function = arguments.callee;
    trace (getFunctionName(callee, this)); // ==> not found
}

private function getFunctionName (callee:Function, parent:Object):String {
    for each ( var m:XML in describeType(parent)..method) {
        if ( parent[m.@name] == callee) return m.@name;
    }
    return "not found";
}

Note that this would not work when you call someFunction() from a constructor, because the object is not fully instantiated - describeType(this) in a constructor would cause a compilation error.

Answer 2

I just did it with a stack trace, which is what the Flash Player debugger shows when an unhandled error is thrown. Here's my implementation:

function blah()
{
    var e:Error = new Error();
    var s:String = e.getStackTrace();
    var functionName:String = s.slice(s.indexOf('/')+1, s.indexOf('('));
    trace(functionName); //blah
}

You'll probably need to make the parsing of the string a bit fancier, if you want to make this a separate function. But the function name is definitely in the stack trace.

Edit: Important Caveat

The AS3 Lang Ref says that the getStackTrace method only works in the Debugger versions of Flash Player/AIR, and will return null otherwise. So this is definitely not a deployable solution. Sorry.