What property can be used to determine when web view fully loaded

Question

I am using a progress bar to illustrate the loading of a webpage via key "estimatedProgress" from observeValueForKeyPath func:

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        // 

        if keyPath == "estimatedProgress"{

            progressView.progress =  Float(webView.estimatedProgress);
    }

My question is there a webView property I can use to determine when the web view has fully loaded so I can reset the progress bar.

Thanks In Advance

So I have implemented following but never seems to be called:

func webViewDidFinishLoad(webView: UIWebView) {
        //set progress abr back to zero, set breakpoint here

        progressView.setProgress(0.0, animated: true);
    }