Foreach loop over a list Scala?

Question

I have a list in scala that looks like the following:

val totalQuote: List[List[String]] = List(List("a","b","c"),List("1","2","3"),List("d","e","f"),List("4","5","6"))

I want to print out every element in the list using a foreach loop. However when I run this:

totalQuote.foreach{ e =>
      val(a,b) = e
      println(a)
    }

I get the following error:

Error:(17, 10) constructor cannot be instantiated to expected type;
 found   : (T1, T2)
 required: List[String]
      val(a,b) = e

Not sure how to resolve this!

Answer 1

You could use nested for -loops:

for {
  list <- totalQuote
  character <- list
} println(character)

Without for , this could also be written as:

totalQuote.foreach { list =>
  list foreach println
}

or even

totalQuote foreach (_ foreach println)

If you want to take only the first two elements out of every list, you could combine for with pattern-matching as follows:

for (a :: b :: _ <- totalQuote) { 
  println(a)
  println(b) 
}

or

for (a :: b :: _ <- totalQuote; x <- List(a, b)) println(x)

Answer 2

The type of e is List[String] but

val (a,b) = e

only works if e is a tuple. Try this

val a::b::_ = e

Answer 3

您可以简单地使用以下命令打印列表中的每个元素

  totalQuote.flatten.foreach{x => println(x)}