[英]Returning all elements from a Map[List()] in Scala
我對 Scala 非常陌生,所以如果聽起來有點基本,我深表歉意。 從事大學作業,似乎找不到任何類似的問題。
編輯:這個 function 的想法是我通過一串數據並將其分成單獨的元素。 據我所知,事情正在與包含正確數據類型和正確信息的列表正確分離。
所以我創建了一個返回 Map[String, List[(Int, String, Float)]] 的 function
function 做其他事情,但為了簡短起見,一旦我建立了列表,這就是我構建 map 並返回它的方式:-
val newMap = Map(name -> newList2.toList)
newMap
我可以 newMap.foreach 循環通過 map 並找到我的所有元素。 這按預期工作: -
(Sample Key,List((3,PlaceName1,2.7)))
(Sample Key,List((2,PlaceName1,3.8)))
(Sample Key,List((1,PlaceName1,0.75)))
我只是想調用這個 function 並將 map 保存到一個新變量中。 我試過這兩種方法: -
val saveMap = separator("1:PlaceName1:0.75,2:PlaceName2:3.8,3:PlaceName3:2.7")
但是,當我嘗試循環瀏覽時,我只得到第一個列表元素:-
(Sample Key,List((1,PlaceName1,0.75)))
我還嘗試使用以下格式的 mapBuffer:-
var mapBuffer: Map[String, List[(Int, String, Float)]] = Map()
mapBuffer = separator("1:PlaceName1:0.75,2:PlaceName2:3.8,3:PlaceName3:2.7")
同樣,我在這里得到的回報是:-
mutated mapBuffer
(Sample Key,List((1,PlaceName1,0.75)))
Being new to Scala but with some experience in Java and C#, it's killing me how I'm returning a Map value, saving it into a map value that is built the same, and it's not coming through. 嘗試了我能找到的地圖和列表的每一次迭代,但在搜索中找不到任何東西。
有人可以提供任何幫助嗎?
編輯:
這是 function 的完整代碼以及我如何嘗試調用它。
def separator(data:String): Map[String, List[(Int, String, Float)]] = {
//Route name will be worked out later. For now, this is a sample.
val sampleRouteName = "First Route"
//Stage list will hold each list entry
val stageList = ListBuffer[(Int, String, Float)]()
//Stage list builder will put all the list entries together
var stageListBuilder = List[(Int, String, Float)]()
if (data.contains(",")) {
//Find index of first comma
val commaIndex = data.indexOf(",")
//Split everything before the comma off
val (firstEntry, restOfPhrase) = data.splitAt(commaIndex)
//Find the index of the colon in the first entry
val colonIndex = firstEntry.indexOf(":")
//Split everything before the colon off to just keep the number
val (number, restOfStage) = firstEntry.splitAt(colonIndex)
//Get rid of the first colon from the rest of the line
val restOfStage2 = restOfStage.replaceFirst(":", "")
//Find the index of the next colon
val colonIndex2 = restOfStage2.indexOf(":")
//Split everything before the colon off to just keep the stage name
val (stageName, restOfStage3) = restOfStage2.splitAt(colonIndex2)
//Get rid of the colon leaving just the stage length
val stageLength = restOfStage3.replaceFirst(":", "")
//Put all of these together into a list line in the builder
stageListBuilder = List((number.toInt,stageName,stageLength.toFloat))
//Add the list line from the builder to the list as an element
stageListBuilder.foreach(line => stageList += line)
//Call recursive function and remove the comma from the start
separator(restOfPhrase.replaceFirst(",", ""))
}
else if (data.length != 0) {
//Find index of first colon
val colonIndex = data.indexOf(":")
//Split everything before the colon off to just keep the number
val (number, restOfStage) = data.splitAt(colonIndex)
//Get rid of the first colon from the rest of the line
val restOfStage2 = restOfStage.replaceFirst(":", "")
//Find the index of the next colon
val colonIndex2 = restOfStage2.indexOf(":")
//Split everything before the colon off to just keep the stage name
val (stageName, restOfStage3) = restOfStage2.splitAt(colonIndex2)
//Get rid of the colon leaving just the stage length
val stageLength = restOfStage3.replaceFirst(":", "")
//Put all of these together into a list line in the builder
stageListBuilder = List((number.toInt,stageName,stageLength.toFloat))
//Add the list line from the builder to the list as an element
stageListBuilder.foreach(line => stageList += line)
}
//This is a map that accurately contains the key (ie. GCU Route) and a list of the routes.
val routeMap = Map(sampleRouteName -> stageList.toList)
//To test that the list has all the elements (CURRENTLY WORKING)
routeMap.foreach(line => println("TEST - " + line))
//Return the map
routeMap
}
//val saveMap = separator("1:City Chambers:0.75,2:Velodrome:3.8,3:People's Palace:2.7")
//Create new map buffer
var mapBuffer: Map[String, List[(Int, String, Float)]] = Map()
//Call separator function
mapBuffer = separator("1:City Chambers:0.75,2:Velodrome:3.8,3:People's Palace:2.7")
//Test that each element is in the list (CURRENTLY NOT WORKING)
mapBuffer.foreach(line => println(line))
正如您所提到的,您使用的密鑰與 Map 的密鑰相同。 假設我們有這樣的分隔符方法:
val str = "1:PlaceName1:0.75,2:PlaceName2:3.8,3:PlaceName3:2.7"
def separator(str: String): List[(String, (Int, String, Float))] =
str.split(",").map(_.split(":")).toList.map(_.toList).collect {
case ii :: s :: d :: Nil =>
"Sample Key" -> (ii.toInt, s, d.toFloat)
}
separator(str).foearch(println)
// result:
(Sample Key,(1,PlaceName1,0.75))
(Sample Key,(2,PlaceName2,3.8))
(Sample Key,(3,PlaceName3,2.7))
如果我們將結果轉換為 Map,我們會丟失一些具有相同鍵的元素,在這種情況下,示例鍵:
def separator1(str: String): Map[String, List[(Int, String, Float)]] =
str.split(",").map(_.split(":")).toList.map(_.toList).collect {
case ii :: s :: d :: Nil =>
"Sample Key" -> List((ii.toInt, s, d.toFloat))
}.toMap
separator1(str).foreach(println)
// result:
// (Sample Key,List((3,PlaceName3,2.7)))
所以我們不能擁有與 Map 的 KEY 相同的密鑰。 Map 的 KEY 應該是唯一的。
case class Aname(a: Int, b: String, c: Float)
def separator2(str: String): Map[String, List[Aname]] =
str.split(",").map(_.split(":")).toList.map(_.toList).collect {
case ii :: s :: d :: Nil =>
Aname(ii.toInt, s, d.toFloat)
}.groupBy(_.b)
separator2(str).foreach(println)
// result:
// (PlaceName3,List(Aname(3,PlaceName3,2.7)))
// (PlaceName2,List(Aname(2,PlaceName2,3.8)))
// (PlaceName1,List(Aname(1,PlaceName1,0.75)))
你可以在這里玩
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