let urlStr = "http://duckduckgo.com"
let urlReq = NSMutableURLRequest(URL: NSURL(string: urlStr)!)
webView.loadRequest(urlReq)

然后,当页面加载完毕后,我想访问html内容

func webViewDidFinishLoad(webView: UIWebView) {
    let href = webView.stringByEvaluatingJavaScriptFromString("window.location.href")
    println("window.location.href  = \(href)")

    let doc = webView.stringByEvaluatingJavaScriptFromString("document")
    println("document = \(doc)")
}

但是文档只返回一个空字符串(Optional(“”)). window.location.href部分工作正常.我做错了什么？