Scala return Map方法的对象类型

我有一个名为“readStock”的函数，它应该返回类型为[String，WeatherReading]的值，而“WeatherReading”是案例类“WeatherReadingStub”的对象。我不知道如何声明和返回函数“readStock”的对象。Scala return Map方法的对象类型

代码： -

package HW9 

object WeatherStub { 
    //Setting file name 
    val fileName = "weather.csv" 
    //Calling Main 
    def main(args: Array[String]): Unit = { 
     val weatherData: Map[String, WeatherReading] = readWeather(fileName) 
      printWeather(weatherData) 
     } 
     def readWeather(fn: String): Map[String,WeatherReading] = { 
      //Creating a mutable map to collect all the values 
      val weatherMuteMap = scala.collection.mutable.Map[String, WeatherReading]() 
      //Checking for empty or null values 
      def IsEmptyOrNull(s: String): Option[Float] = { 
       if ((s ne null) && s.trim.length > 0) Some(s.toFloat) else None 
      } 
      //Reading file 
      for (line <- io.Source.fromFile(fn).getLines()) { 
       val list1 = line.split(",", -1).map(_.trim).toList 
      //Setting up default values 
      val TotalPrecp: Option[Float] = IsEmptyOrNull(list1(1).toString) match { case Some(i) => Some(i) case _ => None} 
      val LowPrecp: Option[Float] = IsEmptyOrNull(list1(2).toString) match { case Some(i) => Some(i) case _ => None} 
      val HighPrecp: Option[Float] = IsEmptyOrNull(list1(3).toString) match { case Some(i) => Some(i) case _ => None} 

      //Creating object for the case class WeatherReadingStub 
      val WeatherReading = WeatherReadingStub(TotalPrecp,LowPrecp,HighPrecp) 

      //Adding elements to the mutable list 
      weatherMuteMap(list1(0).toString) = WeatherReading.toString 
     } 
     //Converting to Immutbale Map 
     weatherMuteMap.toMap 
    } 


    def printWeather(weatherMap: Map[String, String]): Unit = { 
     //Format of the message to be printed 
     println("(Date,{Precipitation,LowTemperature,HighTemperature})\tAverageTemperature") 

     //Printing the average temp values calculated in Case Class using object 
     weatherMap.toSeq.sortBy(_._1).foreach(wd => println(wd + "\t" + wd._2.averageTemperature.getOrElse("N/A"))) 
     println 

    } 

}

案例类代码： -

package HW9 

case class WeatherReadingStub(precipitation: Option[Float], lowTemperature: Option[Float], highTemperature: Option[Float]) { 

    def averageTemperature: Option[Float] = (lowTemperature, highTemperature) match {case (Some(i),Some(j)) => Some((i + j)/2) case _ => None} 

    override def toString: String = s"{${precipitation.getOrElse("MISSING")},${lowTemperature.getOrElse("MISSING")},${highTemperature.getOrElse("MISSING")}}" 
}

来源

2017-04-10 Issaq

通过类型[String，WeatherReading]的值'你是指一个元组吗？ – mfirry

“WeatherReading是案例类WeatherReadingStub的对象”，你的意思是伴侣对象吗？ Companion对象与类名称相同，而'case class'自动创建自己的伴随对象。 – jwvh

如果您遵循[这些有用的指导方针]（http://stackoverflow.com/help/mcve），您会更好，更快地回答您的问题。如果您设置代码的格式，以便我们不必左右滚动来阅读它，这也会很有帮助。 – jwvh

检查你的类名WeatherReadingStub。在Object WeatherStub中， readWeather方法使用关键字date（String类型）和value是WeatherReading对象构建可变Map。您的班级WeatherReadingStub具有averageTemperature，并且您在MAP [String，WeatherReadingStub]中引用了WeatherReadingStub。如果您将WeatherReading替换为您定义的对象WeatherReadingStub，则此程序将运行。您对MAP的定义应该是 val weatherData：Map [String，WeatherReadingStub] = readWeather（fileName）（替换所有其他出现的地方）

来源

2017-04-12 01:18:35

Scala return Map方法的对象类型

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