spark dataframe explode function error
<p>I'd like to use the explode function on a DF, I just write the code like the document:</p>

<pre><code>    case class Url(url:String)
    val temp3 = temp2.explode($"urls"){
        case Row(urls:Array[String]) =&gt; urls.map(Url(_))
    }
</code></pre>

<p>However , it came out:</p>

<pre><code>error: not found: value Row
</code></pre>

<p>The DF temp2 is like:</p>

<pre><code>temp2.printSchema()
root
 |-- userid: string (nullable = true)
 |-- urls: array (nullable = true)
 |    |-- element: string (containsNull = true)
</code></pre>