Question

我有Map[key:String, value:String]和List[(s1:String,s2:String,s3:String)]

我想从整个Row（元组）中获取（提取）第3个字符串第3个字段s3。

主要是它与地图中的键和列表中的3字段行进行一对一映射。

Answer 1

如果您想要在地图中提取其他字段时在元组中提取字段，

您必须.filter通过列表才能匹配Map和
映射以获取元组的必需元素。

例如，

scala> val customers = Map("customer1" -> "location", 
                           "customer2" -> "location2", 
                           "customer-strange" -> "canada-strange")
customers: scala.collection.immutable.Map[String,String] = Map(customer1 -> location, customer2 -> location2, customer-strange -> canada-strange)

scala> val orders = Seq(("customer1", "shirts", "pants"), 
                        ("customer2", "guitar", "drum"), 
                        ("customer-not-in-map", "whatever-1", "whatever-2"))
orders: Seq[(String, String, String)] = List((customer1,shirts,pants), (customer2,guitar,drum), (customer-not-in-map,whatever-1,whatever-2))

scala> orders.collect { case (s1, s2, s3) if customers.contains(s1) => s3 }
res2: Seq[String] = List(pants, drum)

另一个版本是

scala> orders.filter { case (s1, s2, s3) => customers.contains(s1) }
             .map { case (s1, s2, s3) => s3}
res5: Seq[String] = List(pants, drum)

尝试工作示例 - https://scastie.scala-lang.org/prayagupd/Hz4BDU02RQm1AzJZl73lAA/5

如何在列表中搜索Map键：Scala

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