Can I not use yield waitForSeconds in a class function?

I have a class like this:

class ignore {
    var howLong:float = 0;

    function ignore () {}

    function timedIgnore(){
        Debug.Log("ignoring for " + howLong + " seconds");
        yield WaitForSeconds (howLong);
        Debug.Log("done ignoring...");
    }
}

I have this in another game object / script / function:

var iggy = new ignore();
iggy.howLong= 5;
iggy.timedIgnore();

And nothing happens. The Debug.Logs don't appear. If I remove the yield line, both Debug.Logs appear, but, obviously, I want a timer here...

So, is the yield not allowed in a class like this, or am I doing something else wrong?

thanks in advance!

You have to use StartCoroutine explicitly when starting coroutines from classes like that.

StartCoroutine(iggy.timedIgnore());