I'm trying to create a scopt option for Seq[String]:
import scopt._
import scopt.Read._
opt[Seq[String]]("foobar")
^ error
but the compiler complains that it could not find implicit value for evidence parameter of type scopt.Read[Seq[String]].
I'm using Scala 2.11.2 and scopt 3.3.0.
Am I missing an import or something else?
This error seems to be resolved in scopt "3.6.0"
here's what my build.sbt looks like:
scalaVersion := "2.11.8"
libraryDependencies ++= Seq(
"org.apache.spark" % "spark-core_2.11" % "2.1.0" ,
"com.github.scopt" %% "scopt" % "3.6.0")
Looking at the source code, it looks like you just need to import scopt.Read. This will import the Read companion object which contains an implicit to handle this for you:
// reads("1,2,3,4,5") == Seq(1,2,3,4,5)
implicit def seqRead[A: Read]: Read[Seq[A]] = reads { (s: String) =>
s.split(sep).map(implicitly[Read[A]].reads)
}
Note: I have not run this through a REPL to verify, but it should work.
Related
Hi I have a file given to by my teacher. It is about Scala and Spark.
When I run the code it gives me this exception:
(run-main-0) scala.ScalaReflectionException: class java.sql.Date in
JavaMirror with ClasspathFilter
The file itself looks like this:
import org.apache.spark.ml.feature.Tokenizer
import org.apache.spark.sql.Dataset
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.types._
object Main {
type Embedding = (String, List[Double])
type ParsedReview = (Integer, String, Double)
org.apache.log4j.Logger getLogger "org" setLevel
(org.apache.log4j.Level.WARN)
org.apache.log4j.Logger getLogger "akka" setLevel
(org.apache.log4j.Level.WARN)
val spark = SparkSession.builder
.appName ("Sentiment")
.master ("local[9]")
.getOrCreate
import spark.implicits._
val reviewSchema = StructType(Array(
StructField ("reviewText", StringType, nullable=false),
StructField ("overall", DoubleType, nullable=false),
StructField ("summary", StringType, nullable=false)))
// Read file and merge the text abd summary into a single text column
def loadReviews (path: String): Dataset[ParsedReview] =
spark
.read
.schema (reviewSchema)
.json (path)
.rdd
.zipWithUniqueId
.map[(Integer,String,Double)] { case (row,id) => (id.toInt, s"${row getString 2} ${row getString 0}", row getDouble 1) }
.toDS
.withColumnRenamed ("_1", "id" )
.withColumnRenamed ("_2", "text")
.withColumnRenamed ("_3", "overall")
.as[ParsedReview]
// Load the GLoVe embeddings file
def loadGlove (path: String): Dataset[Embedding] =
spark
.read
.text (path)
.map { _ getString 0 split " " }
.map (r => (r.head, r.tail.toList.map (_.toDouble))) // yuck!
.withColumnRenamed ("_1", "word" )
.withColumnRenamed ("_2", "vec")
.as[Embedding]
def main(args: Array[String]) = {
val glove = loadGlove ("Data/glove.6B.50d.txt") // take glove
val reviews = loadReviews ("Data/Electronics_5.json") // FIXME
// replace the following with the project code
glove.show
reviews.show
spark.stop
}
}
I need to keep the line
import org.apache.spark.sql.Dataset
because some code depends on it but it is exactly because of it I have an exception throw.
My build.sbt file looks like this:
name := "Sentiment Analysis Project"
version := "1.1"
scalaVersion := "2.11.12"
scalacOptions ++= Seq("-unchecked", "-deprecation")
initialCommands in console :=
"""
import Main._
"""
libraryDependencies += "org.apache.spark" %% "spark-core" % "2.3.0"
libraryDependencies += "org.apache.spark" %% "spark-mllib" %
"2.3.0"
libraryDependencies += "org.scalactic" %% "scalactic" % "3.0.5"
libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.5" %
"test"
The Scala guide recommends you compile with Java8:
We recommend using Java 8 for compiling Scala code. Since the JVM is backward compatible, it is usually safe to use a newer JVM to run your code compiled by the Scala compiler for older JVM versions.
Although it's only a recommendation, I found it to fix the issue you mention.
In order to install Java 8 using Homebrew, it's best to use jenv which will help you handle multiple Java versions should you need to.
brew install jenv
Then run the following to add a tap (repository) of alternative versions of casks, since Java 8 is not in the default tap anymore:
brew tap homebrew/cask-versions
To install Java 8:
brew cask install homebrew/cask-versions/adoptopenjdk8
Run the following to add the previously installed Java version to jenv's list of versions:
jenv add /Library/Java/JavaVirtualMachines/<installed_java_version>/Contents/Home
Finally run
jenv global 1.8
or
jenv local 1.8
to use Java 1.8 globally or locally (in the current folder).
Fore more information, follow the instructions at jenv's website
Actually learning how to code with scala, I need some help on this:
import play.api.libs.json._
case class Alert(email: String, query: String)
{
def main(args: Array[String]): Unit = { println("Hello from main of class")}
}
I've got an error message :
Alert.scala:2: error: not found: object play
import play.api.libs.json._
One error found
I don't know where the problem come, I updated IntelliJ, and even added the missing library Dependencies in my build.sbt
name := """alert"""
version := "1.0-SNAPSHOT"
lazy val root = (project in file(".")).enablePlugins(PlayScala)
scalaVersion := "2.11.7"
libraryDependencies ++= Seq(
jdbc,cache,ws,
"org.scalatestplus.play" %% "scalatestplus-play" % "1.5.1" % Test,
"org.tpolecat" %% "doobie-core" % "0.4.1",)
I'm quite sure they explained it very well in this related question:
object play not found in scala application
I'm trying to write a test case for a simple REST API in Play2/Scala that send/receives JSON. My test looks like the following:
import org.junit.runner.RunWith
import org.specs2.matcher.JsonMatchers
import org.specs2.mutable._
import org.specs2.runner.JUnitRunner
import play.api.libs.json.{Json, JsArray, JsValue}
import play.api.test.Helpers._
import play.api.test._
import play.test.WithApplication
/**
* Add your spec here.
* You can mock out a whole application including requests, plugins etc.
* For more information, consult the wiki.
*/
#RunWith(classOf[JUnitRunner])
class APIv1Spec extends Specification with JsonMatchers {
val registrationJson = Json.parse("""{"device":"576b9cdc-d3c3-4a3d-9689-8cd2a3e84442", |
"firstName":"", "lastName":"Johnny", "email":"justjohnny#test.com", |
"pass":"myPassword", "acceptTermsOfService":true}
""")
def dropJsonElement(json : JsValue, element : String) = (json \ element).get match {
case JsArray(items) => util.dropAt(items, 1)
}
def invalidRegistrationData(remove : String) = {
dropJsonElement(registrationJson,remove)
}
"API" should {
"Return Error on missing first name" in new WithApplication {
val result= route(
FakeRequest(
POST,
"/api/v1/security/register",
FakeHeaders(Seq( ("Content-Type", "application/json") )),
invalidRegistrationData("firstName").toString()
)
).get
status(result) must equalTo(BAD_REQUEST)
contentType(result) must beSome("application/json")
}
...
However when I attempt to run sbt test, I get the following error:
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=384M; support was removed in 8.0
[info] Loading project definition from /home/cassius/brentspace/esalestracker/project
[info] Set current project to eSalesTracker (in build file:/home/cassius/brentspace/esalestracker/)
[info] Compiling 3 Scala sources to /home/cassius/brentspace/esalestracker/target/scala-2.11/test-classes...
[error] /home/cassius/brentspace/esalestracker/test/APIv1Spec.scala:34: could not find implicit value for evidence parameter of type org.specs2.main.CommandLineAsResult[play.test.WithApplication{val result: scala.concurrent.Future[play.api.mvc.Result]}]
[error] "Return Error on missing first name" in new WithApplication {
[error] ^
[error] one error found
[error] (test:compileIncremental) Compilation failed
[error] Total time: 3 s, completed 18/01/2016 9:30:42 PM
I have similar tests in other applications, but it looks like the new version of specs adds a lot of support for Futures and other things that invalidate previous tutorials. I'm on Scala 2.11.6, Activator 1.3.6 and my build.sbt looks like the following:
name := """eSalesTracker"""
version := "1.0-SNAPSHOT"
lazy val root = (project in file(".")).enablePlugins(PlayScala)
scalaVersion := "2.11.6"
libraryDependencies ++= Seq(
jdbc,
cache,
ws,
"com.typesafe.slick" %% "slick" % "3.1.0",
"org.postgresql" % "postgresql" % "9.4-1206-jdbc42",
"org.slf4j" % "slf4j-api" % "1.7.13",
"ch.qos.logback" % "logback-classic" % "1.1.3",
"ch.qos.logback" % "logback-core" % "1.1.3",
evolutions,
specs2 % Test,
"org.specs2" %% "specs2-matcher-extra" % "3.7" % Test
)
resolvers += "scalaz-bintray" at "http://dl.bintray.com/scalaz/releases"
resolvers += Resolver.url("Typesafe Ivy releases", url("https://repo.typesafe.com/typesafe/ivy-releases"))(Resolver.ivyStylePatterns)
// Play provides two styles of routers, one expects its actions to be injected, the
// other, legacy style, accesses its actions statically.
routesGenerator := InjectedRoutesGenerator
I think you are using the wrong WithApplication import.
Use this one:
import play.api.test.WithApplication
The last line of the testcase should be the assertion/evaluation statement.
e.g. before the last } of the failing testcase method put the statement false must beEqualTo(true) and run it again.
I'm trying to get a simple "hello world" server running using spray with scala 2.11:
import spray.routing.SimpleRoutingApp
import akka.actor.ActorSystem
object SprayTest extends App with SimpleRoutingApp {
implicit val system = ActorSystem("my-system")
startServer(interface = "localhost", port = 8080) {
path("hello") {
get {
complete {
<h1>Say hello to spray</h1>
}
}
}
}
}
However, I receive the following compile errors:
Multiple markers at this line
- not found: value port
- bad symbolic reference to spray.can encountered in class file 'SimpleRoutingApp.class'. Cannot
access term can in package spray. The current classpath may be missing a definition for spray.can, or
SimpleRoutingApp.class may have been compiled against a version that's incompatible with the one
found on the current classpath.
- not found: value interface
Does anyone know what might be the issue? BTW, I'm very new to spray and actors, so I lack a lot of intuition for how spray and actors work (that's why I'm doing this simple tutorial).
Finally found the answer myself. I needed to add the spray-can dependency to my pom file. Leaving this question and answer in case anyone else runs into the same problem.
SBT example:
scalaVersion := "2.10.4"
val akkaVersion = "2.3.6"
val sprayVersion = "1.3.2"
resolvers ++= Seq(
"Spray Repository" at "http://repo.spray.io/"
)
libraryDependencies ++= Seq(
"com.typesafe.akka" %% "akka-actor" % akkaVersion,
"io.spray" %% "spray-can" % sprayVersion,
"io.spray" %% "spray-routing" % sprayVersion
)
I'm trying to map over an HList in shapeless. The following example is derived from here:
import shapeless._
import poly._
object Main {
def main(args: Array[String]) = {
object choose extends (Set ~> Option) {
def apply[T](s : Set[T]) = s.headOption
}
val sets = Set(1) :: Set("foo") :: HNil
val opts = sets map choose // map selects cases of choose for each HList element
}
}
Unfortunately I am unable to compile the example. The compiler says "value map is not a member of HCons[scala.collection.immutable.Set[Int],HCons[scala.collection.immutable.Set[String],HNil]]". I suspect there is a missing import of an implicit that defines the map operation on HLists, but I don't know what that import should be. I'm using sbt with the following build.sbt file:
name := "scala-polymorphism-experiments"
version := "0.1.0"
scalaVersion := "2.10.3"
resolvers ++= Seq(
"Sonatype OSS Releases" at "http://oss.sonatype.org/content/repositories/releases/",
"Sonatype OSS Snapshots" at "http://oss.sonatype.org/content/repositories/snapshots/"
)
libraryDependencies ++= Seq("org.scalatest" % "scalatest_2.10" % "2.0" % "test",
"com.chuusai" % "shapeless" % "2.0.0-SNAPSHOT" cross CrossVersion.full changing())
I also have this problem if I use the M1 release of 2.0.0. What should I change to make this example compile and run?
The problem was never determined. The solution was to comment out all code in all other scala files in the project, recompile, then uncomment and compile again. No doubt an
sbt clean
would have done just as well.