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Question

I am getting compile error when trying to map list of tuples. I have a method which return Future[List[(String, String)]] and I need to use those two set of String value to make a call to another method

def myHelper(): Future[List[(String, String)]] = { ... }

def myWork() = {
  myHelper() map {
    case(firstVal, secondVal) => otherWork(firstVal, secondVal)
  }
} 

Error I am getting is

found: (T1, T2)
required: List[(String, String)]

Any suggestion?

EDIT hmm .... I wasn't clear about my question. otherWork expect list of all result

def otherWork(firstVals: List[String], secondVals: List[Strong]) = { ... }

Answer 1

Depends on what you want to do.

Call otherWork on every tuple?

def myWork() = {
    myHelper().map(_.map {
        case (firstVal, secondVal) => otherWork(firstVal, secondVal)
    })
}

If otherWork: (String, String) => T , then myWork: () => Future[List[T]] .

If otherWork: (String, String) => Future[T] and you want to run them all and collect the results, then you can use something like

def myWork() = {
    myHelper() flatMap { list => Future.sequence(
        list map { case (firstVal, secondVal) =>
            otherWork(firstVal, secondVal)
        })
    }
}

---

With the question clarification, you want unzip .

def myWork() = {
    myHelper() map { list =>
        list.unzip match {
            case (firstVals, secondVals) => otherWork(firstVals, secondVals)
        }
    }
}

Federico Pellegatta's answer has a shorter form of writing this.

Answer 2

Let's implement the myWork function as:

def myWork = myHelper.map {
  helper => (otherWork _).tupled(helper.unzip)
}