Question

我正在研究ScalaInAction中的示例，我无法运行遍布多个文件并放在单个包中的示例。

这是代码。

mongoclient.scala


package com.scalainaction.mongo
import com.mongodb._

class MongoClient(val host:String, val port:Int) {
    require(host != null, "You have to provide a host name")
    val underlying = new com.scalainaction.mongo.Mongo
    def this() = this("127.0.0.1", 27017)
    def version = underlying.getVersion
    def dropDB(name:String) = underlying.dropDatabase(name) 
    def createDB(name:String) = DB(underlying.getDB(name)) 
    def db(name:String) = DB(underlying.getDB(name))
}

DB.scala


package com.scalainaction.mongo
import com.mongodb.{DB => MongoDB}
import scala.collection.convert.Wrappers._

class DB private(val underlying: MongoDB) {
    private def collection(name: String) = underlying.getCollection(name)
    def readOnlyCollection(name: String) = new DBCollection(collection(name)) 

    def administrableCollection(name: String) = new
        DBCollection(collection(name)) with Administrable

    def updatableCollection(name: String) = new
        DBCollection(collection(name)) with Updatable

    def collectionNames = for(name



DBCollection.scala


package com.scalainaction.mongo
import com.mongodb.{DBCollection => MongoDBCollection } 
import com.mongodb.DBObject

class DBCollection(override val underlying: MongoDBCollection) extends ReadOnly

trait ReadOnly {
  val underlying: MongoDBCollection
  def name = underlying.getName
  def fullName = underlying.getFullName
  def find(doc: DBObject) = underlying.find(doc)
  def findOne(doc: DBObject) = underlying.findOne(doc)
  def findOne = underlying.findOne
  def getCount(doc: DBObject) = underlying.getCount(doc)
}

trait Administrable extends ReadOnly {
  def drop: Unit = underlying.drop
  def dropIndexes: Unit = underlying.dropIndexes
}

trait Updatable extends ReadOnly {
  def -=(doc: DBObject): Unit = underlying.remove(doc)
  def +=(doc: DBObject): Unit = underlying.save(doc)
}



All the programs are placed inside the same package 
com.scalainaction.mongo. 

I don't use an IDE so I compile these files by running


scalac mongoclient.scala DB.scala DBCollection.scala



My $CLASSPATH includes the mongodb.jar file and also points to com.scalainaction.mongo folder in my application directory

package com.scalainaction.mongo import com.mongodb.{DBCollection => MongoDBCollection } import com.mongodb.DBObject class DBCollection(override val underlying: MongoDBCollection) extends ReadOnly trait ReadOnly { val underlying: MongoDBCollection def name = underlying.getName def fullName = underlying.getFullName def find(doc: DBObject) = underlying.find(doc) def findOne(doc: DBObject) = underlying.findOne(doc) def findOne = underlying.findOne def getCount(doc: DBObject) = underlying.getCount(doc) } trait Administrable extends ReadOnly { def drop: Unit = underlying.drop def dropIndexes: Unit = underlying.dropIndexes } trait Updatable extends ReadOnly { def -=(doc: DBObject): Unit = underlying.remove(doc) def +=(doc: DBObject): Unit = underlying.save(doc) }


import com.scalainaction.mongo._
import com.mongodb.BasicDBObject

def client = new MongoClient("127.0.0.1", 27017)
def db = client.db("mydb")

for(name

但我的应用程序无法找到MongoClient类，我收到此错误

quickTour.scala:1: error: object scalainaction is not a member of package com
import com.scalainaction.mongo._
           ^
/Users/sid/scala_apps/quickTour.scala:4: error: MongoClient does not have a constructor
def client = new MongoClient("127.0.0.1", 27017)
             ^
two errors found

我不遵循为什么它找不到构造函数。我用def this方法定义了一个重载的构造函数

为什么找不到com.scalanation.mongo？

我将不胜感激任何帮助

**更新**

我的com / scalainaction / mongo文件夹中的文件是

Administrable$class.class       DB$.class               ReadOnly$class.class
Administrable.class         DB.class                ReadOnly.class
DB$$anon$1.class            DBCollection.class          Updatable$class.class
DB$$anon$2.class            MongoClient$$anonfun$1.class        Updatable.class
DB$$anonfun$collectionNames$1.class MongoClient.class

Answer 1

问题是您的文件夹com和/或com / scalainaction为空。在那里放一些课，它应该有用。

Scala初学者在多个文件上编译和运行scala程序

1 个答案: