QML TableView: Component.onCompleted runs twice for each rowDelegate

The below simple Component, used as a rowDelegate for a TableView, should
illustrate the problem. When I run this I get 66 console messages reporting
that styleData is unavailable, followed by 66 console messages reporting
that styleData is available. As long as I test for a completed styleData within the handler, my app runs fine. Incidentally, if I then immediately
exit the application, I get 66 more console messages again reporting that
styleData is unavailable.

Component {
   id: tableRowDelegate

      Rectangle {
         id: tableRow

         Component.onCompleted: {

           if ("row" in styleData)
             console.log("styleData available for row(" + styleData.row + ")")
           else
             console.log("styleData unavailable for row(unavailable)")
         }
      }
   }