如何將List [List [Map [String，String]]]轉換爲List [Map [String，String]]

Question

我有類型List[List[Map[String,String]]]的結果，我想將它轉換爲List[Map[String,String]]。我如何在Scala中做到這一點？

Answer 1

這是幫助我瞭解如何扁平化的工作。

val a = List(List(Map(11 -> 11), Map(12 -> 12)), List(Map(21 -> 21), Map(21 -> 21))) 

def flatten(ls: List[Any]): List[Any] = ls flatMap { 
    case ms: List[_] => flatten(ms) 
    case e => List(e) 
} 

flatten(a) 

/** Converts this $coll of traversable collections into 
    * a $coll in which all element collections are concatenated. 
    * 
    * @tparam B the type of the elements of each traversable collection. 
    * @param asTraversable an implicit conversion which asserts that the element 
    *   type of this $coll is a `Traversable`. 
    * @return a new $coll resulting from concatenating all element ${coll}s. 
    * @usecase def flatten[B]: $Coll[B] 
    */ 
def flatten[B](implicit asTraversable: A => /*<:<!!!*/ TraversableOnce[B]): CC[B] = { 
    val b = genericBuilder[B] // incrementally build 
    for (xs <- sequential) // iterator for your collection 
     b ++= asTraversable(xs) // am i traversable ? 
    b.result     // done ... build me 
} 

Answer 2

給出無約束：

list.flatten