如何递归地附加到DBObjectCasbah 中的 a ，然后返回一个MongoDBObject附加了每个列表元素的单个？
请注意，以下内容无法编译或工作，但它旨在显示我想要的代码
def foo( pairs: List[(String, Int)]): List[MongoDBObject] = {
def go( ps: List[(String, Int)], acc: List[MongoDBObject]): List[MongoDBObject] =
ps match {
case x :: xs if(x._1 == "BAD") => go(xs, acc)
case x :: xs => go(xs, MongoDBObject(x._1 -> x._2) :+ acc) /* error line */
case Nil => acc
}
}
val pairsList: List[MongoDBObject] = foo( getPairs() ) // assume getPairs() is defined
val builder = // do something to convert pairsList -> MongoDBObject (maybe a fold?)
val results = collection.find(builder)
当我尝试上述方法时，我在第二个 case 语句中看到了以下编译时错误。
[myApp] $ compile
[info] Compiling 1 Scala source to ...
[error] c:\development\myApp\Test.scala:85: overloaded method value apply with alternatives:
[error] [A(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply) <
: String, B(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)](e
lems: List[(A(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply),
B(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply))])com.mongo
db.casbah.commons.Imports.DBObject <and>
[error] [A(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply) <
: String, B(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)](e
lems: (A(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply), B(in
method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply)(in method apply))*)com.mongodb.ca
sbah.commons.Imports.DBObject
[error] cannot be applied to (com.mongodb.casbah.query.Imports.DBObject with com.mongodb.casbah.query.dsl.QueryExpressionObject)
[error] go(xs, acc :+ MongoDBObject(elemMatch))
[error] ^
[error] one error found