好的，这个问题似乎真的很愚蠢，但我的观点是，如果你看一下Scala 2.7.6 API，他们就不推荐使用mappingToString方法了。因此，应该有更优雅的替代方案来打印自定义格式的Map。因为几乎任何目的，在Map中使用mkString的等价方法非常方便。
你们怎么看待它？打印除println以外的地图的编码片段是什么？
答案 0 :(得分：3)
mappingToString特定于Map。
使用Scala2.8中的新集合框架，任何Map都可以迭代IterableLike，mkstring()扩展/*
Making use of raw strings to create a multi line string
I add a | at the beginning of each line so that we can line up the quote nicely
in source code then later strip it from the string using stripMargin
*/
scala> val quote = """|I don-t consider myself a pessimist.
| |I think of a pessimist as someone who is waiting for it to rain.
| |And I feel soaked to the skin.
|
| |Leonard Cohen"""
quote: java.lang.String =
|I don-t consider myself a pessimist.
|I think of a pessimist as someone who is waiting for it to rain.
|And I feel soaked to the skin.
|Leonard Cohen
// capilize the first character of each line
scala> val capitalized = quote.lines.
| map( _.trim.capitalize).mkString("\n")
capitalized: String =
|I don-t consider myself a pessimist.
|I think of a pessimist as someone who is waiting for it to rain.
|And I feel soaked to the skin.
|Leonard Cohen
// remove the margin of each line
scala> quote.stripMargin
res1: String =
I don-t consider myself a pessimist.
I think of a pessimist as someone who is waiting for it to rain.
And I feel soaked to the skin.
Leonard Cohen
// this is silly. I reverse the order of each word but keep the words in order
scala> quote.stripMargin.
| lines.
| map( _.split(" ").
| map(_.reverse).
| mkString (" ")).
| mkString("\n")
res16: String =
I t-nod redisnoc flesym a .tsimissep
I kniht fo a tsimissep sa enoemos ohw si gnitiaw rof ti ot .niar
dnA I leef dekaos ot eht .niks
dranoeL nehoC
。
然后应该使用方法TraversableLike（已经存在于mkstring的2.7中）。
有关2.7 {{1}}示例的信息，请参阅此Iterable：
{{1}}
答案 1 :(得分：3)
mappingToString方法用于更改每对键/值转换为String的方式，然后由toString方法使用。
我觉得这很糟糕。一方面，它为其他不可变数据结构添加了可变性。如果您有特定的打印要求，那么最好将它们放在另一个类中。
答案 2 :(得分：3)
您还可以将Iterator.map()与mkString()合并，例如从map[String,String]创建查询字符串：
val queryString = updatedMap.map(pair => pair._1+"="+pair._2).mkString("?","&","")