title: Rich function on Flink join, Scala API
body: <p>I'm struggling with Flink and Scala.</p>
  
  <p>I have a join transformation over a <code>DataSet</code> that pretty much works, but I want to turn it into a <code>RichFuntion</code>, so that I can access a broadcasted set:</p>
  
  <pre><code>val newBoard: DataSet[Cell] = board.rightOuterJoin(neighbours)
                               .where("coords").equalTo("cellCoords"){
  
      (cell, neighbours) =&gt; {
              // Do some rich function things, like 
              // override the open method so I can get
              // the broadcasted set
      }
  
    }
  
  }.withBroadcastSet(board, "aliveCells")
  </code></pre>
  
  <p>I have been looking all over the documentation, but I can't find any example of a <code>RichJoinFuntion</code> being used in Scala. I only find <a href="https://ci.apache.org/projects/flink/flink-docs-master/apis/batch/index.html#broadcast-variables" rel="nofollow">examples</a> for rich functions used in <code>map</code> or <code>filter</code>, but the syntax is different for the <code>join</code> transformation (function between parenthesis vs. between brackets).</p>