Updating a string variable from within nested for loop in Scala-CodePudding

I have a Dataframe which I am trying converting to html table syntax as a string in Scala:

sample_df: which is of type DataFrame = Dataset[Row]

|Name|Country|Occupation|Years_Experience|
|Bob |USA    | Engineer |  5             |
|John|CANADA | Sales    |  3             |

I already have the html headers converted however need to have the html rows and values in a string variable as below html_string:

<tr>
      <td>Bob</td>
      <td>USA</td>
      <td>Engineer</td>
      <td>5</td>
</tr>
<tr>
      <td>John</td>
      <td>CANADA</td>
      <td>Sales</td>
      <td>3</td>
</tr>

However when I try nested loop method below, the html_string variable is not being updated to what I am expecting above. It results in a blank. What am I doing wrong?

Code Attempt:

  var html_string = """"""

  for (i <- sample_df) {
    html_string = html_string   "<tr>"
    for (g <- i.toSeq)  {
      html_string = html_string   "<td>"   g   "</td>"
    }
    html_string = html_string   "</tr>"
  }
  println(html_string)

Thanks!

CodePudding user response：

Not sure what you mean by "dataframe" in this context (you can't iterate spark dataframes like this), but assuming you are talking about a normal sequence, this works for me.

Having said that, this is a very bad way of doing this in scala. The basic rule of thumb when writing scala code is never use mutable variables unless. you know exactly why you must in a specific case (which is extremely rare).

   val html_string = df
     .map { _.mkString("<td>", "</td><td>", "</td>" }
     .mkString("<tr>", "</tr><tr>",  "</tr>")