How to create case class from List[String]? - scala

Question

Here is my code
scala> s
res6: String = 2005-05-06 14:58:56 192 45.14.5.238 200 TCP_NC_MISS 1123 496 GET http c4.maxserving.com /gen.js ?site=5835&area=side_ros&group=sidebar&PageID=33364329499 - DIRECT c4.maxserving.com application/x-javascript "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322)" PROXIED Web%20Advertisements - 192.16.170.44 SG-HTTP-Service - none -
scala> s.split("\\s")
res7: Array[String] = Array(2005-05-06, 14:58:56, 192, 45.14.5.238, 200, TCP_NC_MISS, 1123, 496, GET, http, c4.maxserving.com, /gen.js, ?site=5835&area=side_ros&group=sidebar&PageID=33364329499, -, DIRECT, c4.maxserving.com, application/x-javascript, "Mozilla/4.0, (compatible;, MSIE, 6.0;, Windows, NT, 5.1;, SV1;, .NET, CLR, 1.1.4322)", PROXIED, Web%20Advertisements, -, 192.16.170.44, SG-HTTP-Service, -, none, -)
scala> case class BlueCoatEvent(date: String,
| time: String,
| timeTaken: String,
| cIp: String,
| scStatus: String,
| sAction: String,
| scBytes: String,
| csBytes: String,
| csMethod: String,
| csUriScheme: String,
| csHost: String,
| csUriPath: String,
| csUriQuery: String,
| csUsername: String,
| sHierarchy: String,
| sSupplierName: String,
| rsContentType: String,
| csUserAgent: String,
| scFilterResult: String,
| scFilterCategory: String,
| xVirusId: String,
| sIp: String,
| sSiteName: String,
| xVirusDetails: String,
| xIcapErrorCode: String,
| xIcapErrorDetails: String)
defined class BlueCoatEvent
scala>
How do I create blueCoatEvent from s.split("\\s")?

Answer 1

See answer in Instantiating a case class from a list of parameters
Introduce meaningsful sub-types/case classes and compose BlueCoatEvent with them.

Answer 2

The ugly horrible way is this:
scala> case class A(x: String, y: String, z: String)
defined class A
scala> def toTuple[A <: Object](as:List[A]):Product = {
| val tupleClass = Class.forName("scala.Tuple" + as.size)
| tupleClass.getConstructors.apply(0).newInstance(as:_*).asInstanceOf[Product]
| }
toTuple: [A <: Object](as: List[A])Product
scala> val l = List("a", "b", "c")
l: List[String] = List(a, b, c)
scala> val t3 = toTuple(l).asInstanceOf[Tuple3[String, String, String]]
t3: (String, String, String) = (a,b,c)
scala> val f = A.tupled
f: ((String, String, String)) => A = <function1>
scala> f(t3)
res0: A = A(a,b,c)
You can use any way you want to convert from collection to TupleN:
Convert a Scala list to a tuple?
Is there way to create tuple from list(without codegeneration)?
I picked toTuple from there.
This is unsafe, ugly and does not save you much. You can resort to code generation, reflection or macros to get something more helpful.
Another option:
Based on this idea Applying an argument list to curried function using foldLeft in Scala we can use A.curried with HList to produce a cleaner solution:
object CaseClassFromList extends App {
sealed trait HList
final case class HCons[H, T <: HList](head : H, tail : T) extends HList {
def ::[H1](h : H1) = HCons(h, this)
override def toString = head+" :: "+tail.toString
}
trait HNil extends HList {
def ::[H1](h : H1) = HCons(h, this)
override def toString = "HNil"
}
case object HNil extends HNil
type ::[H, T <: HList] = HCons[H, T]
trait FoldCurry[L <: HList, F, Out] {
def apply(l : L, f : F) : Out
}
// Base case for HLists of length one
implicit def foldCurry1[H, Out] = new FoldCurry[H :: HNil, H => Out, Out] {
def apply(l : H :: HNil, f : H => Out) = f(l.head)
}
// Case for HLists of length n+1
implicit def foldCurry2[H, T <: HList, FT, Out]
(implicit fct : FoldCurry[T, FT, Out]) = new FoldCurry[H :: T, H => FT, Out] {
def apply(l : H :: T, f : H => FT) = fct(l.tail, f(l.head))
}
// Public interface ... implemented in terms of type class and instances above
def foldCurry[L <: HList, F, Out](l : L, f : F)
(implicit fc : FoldCurry[L, F, Out]) : Out = fc(l, f)
case class A(x: String, y: String, z: String)
//val l = List("a", "b", "c")
val lh = "a" :: "b" :: "c" :: HNil
val newA = foldCurry(lh, A.curried)
println(newA)
}
The problem again is that you can't get away from spelling out the types whether those are Tuple or HList unless you go unsafe way or some sort of code generation.

Answer 3

A different approach by defining a Map[String,String] over the values of an event; let
case class EventMap( data: Map[String,String])
and
def fields(cc: Product) = cc.getClass.getDeclaredFields.map(_.getName)
Then from
EventMap( fields(BlueCoatEvent) zip s.split("\\s") toMap )
we can fetch values properties for a given stringisized BlueCoatEvent.