Question

I’m really new to Scala and I’m not even able to concatenate Strings. Here is my code:

object RandomData {

private[this] val bag = new scala.util.Random

def apply(sensorId: String, stamp: Long, size: Int): String = {
  var cpt: Int = 0
  var data: String = "test"
  repeat(10) {
    data += "_test"
  }
  return data
}
}

I got the error:

type mismatch;
 found   : Unit
 required: com.excilys.ebi.gatling.core.structure.ChainBuilder

What am I doing wrong ??

Answer 1

repeat is offered by Gatling in order to repeat Gatling tasks, e.g., query a website. If you have a look at the documentation (I wasn’t able to find a link to the API doc of repeat), you’ll see that repeat expects a chain, which is why your error message says “required: com.excilys.ebi.gatling.core.structure.ChainBuilder”. However, all you do is to append to a string – which will not return a value of type ChainBuilder.

Moreover, appending to a string is nothing that should be done via Gatling. It looks to me as if you are confusing Gatling’s repeat with a Scala for loop. If you only want to append "_test" to data 10 times, use one of Scala’s loops (for, while) or a functional approach with e.g. foldLeft. Here are two examples:

/* Imperative style loop */
for(i <- 1 to 10) {
  data += "_test"
}

/* Functional style with lazy streams */
data += Stream.continually("_test").take(10).mkString("")