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
Related
I just set up a new scala project with sbt in IntelliJ, and wrote the following basic class:
Person.scala:
package learning.functional
case class Person(
name: String
)
Main.scala:
package learning.functional
import learning.functional.person
object Main{
val p = Person("John")
}
PersonTest.scala:
import learning.functional.Person
import org.scalatest.FunSuite
class PersonTest extends FunSuite {
test("test person") {
val p = Person("John")
assert(p.name == "John")
}
}
When I try to run sbt test, it throws the following error:
## Exception when compiling 1 sources to /Users/johndooley/Desktop/Scala/scala-learning/target/scala-2.13/test-classes
[error] java.lang.AssertionError: assertion failed:
[error] unexpected value engine in trait FunSuite final <expandedname> private[this]
[error] while compiling: /Users/johndooley/Desktop/Scala/scala-learning/src/test/scala/PersonTest.scala
What could be the reason for this? My build.sbt file:
ThisBuild / scalaVersion := "2.13.10"
libraryDependencies += "org.scalatest" % "scalatest_2.10" % "1.9.1"
lazy val root = (project in file("."))
.settings(
name := "scala-learning"
)
Project structure:
I have tried invalidating cache and restarting, doing clean, update, compile, but nothing works.
I solved this by modifying my dependency to the following:
libraryDependencies += "org.scalatest" %% "scalatest" % "3.2.14"
and completely reloading the sbt shell
I have the snippet of test case below under src/test/scala:
package example.module
import utest._
object ModuleSpec extends TestSuite { ... }
... which compiles just fine with this snippet of build.sbt below:
val testDependencies: Seq[ModuleID] =
Seq(
"com.lihaoyi" %% "utest" % "0.6.5" % "test",
)
def testSettings: Seq[Setting[_]] =
Seq(
libraryDependencies ++= testDependencies)
lazy val root =
(project in file("."))
.aggregate(subproject)
lazy val subproject =
(project in file("subproject"))
.settings(testSettings: _*)
My question is:
Why the test code does not compile anymore if I add Test axis to libraryDependencies, like shown below?
def testSettings: Seq[Setting[_]] =
Seq(
libraryDependencies in Test ++= testDependencies)
In more detail:
The line containing import utest._ fails to compile, meaning that the dependency which is now declared as part of libraryDependencies in Test was ignored.
Argumentation:
Since I'm compiling a class under src/main/test, I would expect that libraryDependencies in Test would be the necessary and the sufficient piece of information in this case. In order words: I would not expect that a wider scope would be needed.
I'm getting the following error when compiling the following toy class:
package com.example
import scala.tools.reflect.ToolBox
import scala.reflect.runtime.{currentMirror => m}
object Hello {
def main(args: Array[String]): Unit = {
println("Hello, world!")
}
}
[info] Loading project definition from /Users/me/Temp/Bar/project
[info] Set current project to Bar (in build file:/Users/me/Temp/Bar/)
[info] Compiling 1 Scala source to /Users/me/Temp/Bar/target/scala-2.11/classes...
[error] /Users/me/Temp/Bar/src/main/scala/com/example/Hello.scala:3: object tools is not a member of package scala
[error] import scala.tools.reflect.ToolBox
[error] ^
[error] one error found
[error] (compile:compileIncremental) Compilation failed
This is my build.sbt file:
name := """Bar"""
version := "1.0"
scalaVersion := "2.11.8"
// Change this to another test framework if you prefer
libraryDependencies += "org.scalatest" %% "scalatest" % "2.2.4" % "test"
libraryDependencies += "org.scala-lang" % "scala-reflect" % "2.11.8"
// Uncomment to use Akka
//libraryDependencies += "com.typesafe.akka" %% "akka-actor" % "2.3.11"
The following dependency fixed the issue:
libraryDependencies += "org.scala-lang" % "scala-compiler" % "2.11.8"
Is this the best solution?
The ToolBox class is part of the compiler, not the public reflection API.
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.
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.