I built my own idea to strongly typecast the final product, more than the reading stage itself..which as pointed out might be better handled as stage one with something like Apache CSV, and stage 2 could be what i've done. Here's the code you are welcome to it. The idea is to typecast the CSVReader[T] with type T .. upon construction, you must supply the reader with a Factor object of Type[T] as well. The idea here is that the class itself (or in my example a helper object) decides the construction detail and thus decouples this from the actual reading. You could use Implicit objects to pass the helper around but I've not done that here. The only downside is that each row of the CSV must be of the same class type, but you could expand this concept as needed.
class CsvReader/**
* @param fname
* @param hasHeader : ignore header row
* @param delim : "\t" , etc
*/
[T] ( factory:CsvFactory[T], fname:String, delim:String) {
private val f = Source.fromFile(fname)
private var lines = f.getLines //iterator
private var fileClosed = false
if (lines.hasNext) lines = lines.dropWhile(_.trim.isEmpty) //skip white space
def hasNext = (if (fileClosed) false else lines.hasNext)
lines = lines.drop(1) //drop header , assumed to exist
/**
* also closes the file
* @return the line
*/
def nextRow ():String = { //public version
val ans = lines.next
if (ans.isEmpty) throw new Exception("Error in CSV, reading past end "+fname)
if (lines.hasNext) lines = lines.dropWhile(_.trim.isEmpty) else close()
ans
}
//def nextObj[T](factory:CsvFactory[T]): T = past version
def nextObj(): T = { //public version
val s = nextRow()
val a = s.split(delim)
factory makeObj a
}
def allObj() : Seq[T] = {
val ans = scala.collection.mutable.Buffer[T]()
while (hasNext) ans+=nextObj()
ans.toList
}
def close() = {
f.close;
fileClosed = true
}
} //class
next the example Helper Factory and example "Main"
trait CsvFactory[T] { //handles all serial controls (in and out)
def makeObj(a:Seq[String]):T //for reading
def makeRow(obj:T):Seq[String]//the factory basically just passes this duty
def header:Seq[String] //must define headers for writing
}
/**
* Each class implements this as needed, so the object can be serialized by the writer
*/
case class TestRecord(val name:String, val addr:String, val zip:Int) {
def toRow():Seq[String] = List(name,addr,zip.toString) //handle conversion to CSV
}
object TestFactory extends CsvFactory[TestRecord] {
def makeObj (a:Seq[String]):TestRecord = new TestRecord(a(0),a(1),a(2).toDouble.toInt)
def header = List("name","addr","zip")
def makeRow(o:TestRecord):Seq[String] = {
o.toRow.map(_.toUpperCase())
}
}
object CsvSerial {
def main(args: Array[String]): Unit = {
val whereami = System.getProperty("user.dir")
println("Begin CSV test in "+whereami)
val reader = new CsvReader(TestFactory,"TestCsv.txt","\t")
val all = reader.allObj() //read the CSV info a file
sd.p(all)
reader.close
val writer = new CsvWriter(TestFactory,"TestOut.txt", "\t")
for (x<-all) writer.printObj(x)
writer.close
} //main
}
Example CSV (tab seperated.. might need to repair if you copy from an editor)
Name Addr Zip "Sanders, Dante R." 4823 Nibh Av. 60797.00 "Decker, Caryn G." 994-2552 Ac Rd. 70755.00 "Wilkerson, Jolene Z." 3613 Ultrices. St. 62168.00 "Gonzales, Elizabeth W." "P.O. Box 409, 2319 Cursus. Rd." 72909.00 "Rodriguez, Abbot O." Ap #541-9695 Fusce Street 23495.00 "Larson, Martin L." 113-3963 Cras Av. 36008.00 "Cannon, Zia U." 549-2083 Libero Avenue 91524.00 "Cook, Amena B." Ap
#668-5982 Massa Ave 69205.00
And finally the writer (notice the factory methods require this as well with "makerow"
import java.io._
class CsvWriter[T] (factory:CsvFactory[T], fname:String, delim:String, append:Boolean = false) {
private val out = new PrintWriter(new BufferedWriter(new FileWriter(fname,append)));
if (!append) out.println(factory.header mkString delim )
def flush() = out.flush()
def println(s:String) = out.println(s)
def printObj(obj:T) = println( factory makeRow(obj) mkString(delim) )
def printAll(objects:Seq[T]) = objects.foreach(printObj(_))
def close() = out.close
}