type mismatch in nested functions-CodePudding

Objective:- Retrieve json object from aws s3 bucket. Retry on failure. If retry attempts are exhausted, send the error message to azure's event hub.

//Retry function

def retry[T](n: Int, id: String)(fn: => T): Option[T]  = { 
        Try(fn) match {
        case Success(x) => Some(x)
        case Failure(e) => {
        Thread.sleep(1000)
          if (n > 1) {
           retry(n - 1, id)(fn)
          } else {
            val eMessage = "TransactionId ="   id   " : ".concat(e.toString())
            SendMessage(eMessage, event_hub_client)
            None
            }
          }    
        }
      }

//Main function (with above retry) to retrieve objects from aws s3 bucket

 def getS3Object(s3ObjectName: String, s3Client: AmazonS3, evtClient: EventHubClient): String = {
        retry(2,s3ObjectName) {
          val inputS3Stream = s3Client.getObject("my_s3_bucket", s3ObjectName).getObjectContent
          val inputS3String = IOUtils.toString(inputS3Stream, "UTF-8")
          return inputS3String
        }
      }

I get the below compilation failed message:-

error: type mismatch
found : Option[Nothing]
required: String
retry2(2,s3ObjectName)

How to declare the return types of the retry and main functions so that they match?

CodePudding user response：

In terms of types retry look's okay. You need to adapt your other method.

Either make it return a Option[String] or use getOrElse(..) if you want to fallback to some other value.

 def getS3Object(s3ObjectName: String, s3Client: AmazonS3, evtClient: EventHubClient): Option[String] = {
        retry(2,s3ObjectName) {
          val inputS3Stream = s3Client.getObject("my_s3_bucket", s3ObjectName).getObjectContent
          val inputS3String = IOUtils.toString(inputS3Stream, "UTF-8")
          inputS3String
        }
      }

Notice the removal of return keyword which is useless and doesn't do what you think it does (I'll let you search on this topic by yourself).