对于我自己（主要是教学 - 理解光滑背后的黑魔法和scala的反射API）的目的，我想创建一个能够创建表的函数，如果数据库中缺少该表，这样的API：
class Raws(tag: Tag) extends Table[Raw](tag, "raw") {
def id = column[Int]("ID", O.PrimaryKey)
def subject = column[String]("subject")
def xml = column[String]("xml")
def * = (id.?, subject, xml) <> ((Raw.apply _).tupled, Raw.unapply)
}
createTable[Raws](database)
我的尝试是这样的：
def createTable[T <: Table[R], R](dat: Database)(implicit session: Session, tag: TypeTag[T], tag2: TypeTag[R]) = {
val q = TableQuery[T]
dat.run(MTable.getTables(q.baseTableRow.tableName)).map { tables =>
if (tables.toList.isEmpty) {
q2.schema.create
q.schema.create
}
}
}
其中，我想应该运行，但会产生以下输出（scala 2.11.7）：
编译
[error] /Users/avandra/projects/freelancer/dmarcreport/src/main/scala/DMarcReportReader.scala:76: class type required but T found
[error] val q2 = TableQuery[T]
[error] ^
[error] one error found
[error] (compile:compile) Compilation failed
[error] Total time: 1 s, completed Sep 14, 2015 3:18:19 PM
开启宏调试：
[info] Compiling 3 Scala sources to /scalaproject/target/scala-2.11/classes...
performing macro expansion scala.slick.`package`.driver.PostgresDriver.simple.TableQuery.apply[T] at source-/scalaproject/src/main/scala/DMarcReportReader.scala,line-75,offset=2090
TableQuery.apply[T](((tag: Tag) => new T(tag)))
Apply(TypeApply(Select(Ident(slick.lifted.TableQuery), TermName("apply")), List(TypeTree())), List(Function(List(ValDef(Modifiers(PARAM), TermName("tag"), Ident(slick.lifted.Tag), EmptyTree)), Apply(Select(New(TypeTree()), termNames.CONSTRUCTOR), List(Ident(TermName("tag")))))))
[error] /scalaproject/src/main/scala/DMarcReportReader.scala:75: class type required but T found
[error] val q2 = TableQuery[T]
[error] ^
performing macro expansion `package`.this.materializeTypeTag[db.Raws](scala.reflect.runtime.`package`.universe) at source-/scalaproject/src/main/scala/DMarcReportReader.scala,line-119,offset=3802
{
val $u: reflect.runtime.universe.type = scala.reflect.runtime.`package`.universe;
val $m: $u.Mirror = scala.reflect.runtime.`package`.universe.runtimeMirror(this.getClass().getClassLoader());
$u.TypeTag.apply[db.Raws]($m, {
final class $typecreator1 extends TypeCreator {
def <init>(): $typecreator1 = {
$typecreator1.super.<init>();
()
};
def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
val $u: U = $m$untyped.universe;
val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
$m.staticClass("db.Raws").asType.toTypeConstructor
}
};
new $typecreator1()
})
}
Block(List(ValDef(Modifiers(), TermName("$u"), TypeTree().setOriginal(SingletonTypeTree(Select(Select(Select(Select(Ident(scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), TermName("universe")))), Select(Select(Select(Select(Ident(scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), TermName("universe"))), ValDef(Modifiers(), TermName("$m"), TypeTree().setOriginal(Select(Ident(TermName("$u")), TypeName("Mirror"))), Apply(Select(Select(Select(Select(Select(Ident(scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), TermName("universe")), TermName("runtimeMirror")), List(Apply(Select(Apply(Select(This(TypeName("DMarcReportReader")), TermName("getClass")), List()), TermName("getClassLoader")), List()))))), Apply(TypeApply(Select(Select(Ident(TermName("$u")), TermName("TypeTag")), TermName("apply")), List(TypeTree())), List(Ident(TermName("$m")), Block(List(ClassDef(Modifiers(FINAL), TypeName("$typecreator1"), List(), Template(List(Ident(scala.reflect.api.TypeCreator)), noSelfType, List(DefDef(Modifiers(), termNames.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(Apply(Select(Super(This(TypeName("$typecreator1")), typeNames.EMPTY), termNames.CONSTRUCTOR), List())), Literal(Constant(())))), DefDef(Modifiers(), TermName("apply"), List(TypeDef(Modifiers(PARAM), TypeName("U"), List(), TypeTree().setOriginal(TypeBoundsTree(TypeTree().setOriginal(Ident(scala.Nothing)), TypeTree().setOriginal(CompoundTypeTree(Template(List(Ident(scala.reflect.api.Universe), Ident(scala.Singleton)), noSelfType, List()))))))), List(List(ValDef(Modifiers(PARAM), TermName("$m$untyped"), TypeTree().setOriginal(AppliedTypeTree(Ident(scala.reflect.api.Mirror), List(TypeTree().setOriginal(Ident(TypeName("U")))))), EmptyTree))), TypeTree().setOriginal(SelectFromTypeTree(TypeTree().setOriginal(Ident(TypeName("U"))), TypeName("Type"))), Block(List(ValDef(Modifiers(), TermName("$u"), TypeTree().setOriginal(Ident(TypeName("U"))), Select(Ident(TermName("$m$untyped")), TermName("universe"))), ValDef(Modifiers(), TermName("$m"), TypeTree().setOriginal(Select(Ident(TermName("$u")), TypeName("Mirror"))), TypeApply(Select(Ident(TermName("$m$untyped")), TermName("asInstanceOf")), List(TypeTree().setOriginal(Select(Ident(TermName("$u")), TypeName("Mirror"))))))), Select(Select(Apply(Select(Ident(TermName("$m")), TermName("staticClass")), List(Literal(Constant("db.Raws")))), TermName("asType")), TermName("toTypeConstructor")))))))), Apply(Select(New(Ident(TypeName("$typecreator1"))), termNames.CONSTRUCTOR), List())))))
performing macro expansion `package`.this.materializeTypeTag[db.Raw](scala.reflect.runtime.`package`.universe) at source-/scalaproject/src/main/scala/DMarcReportReader.scala,line-119,offset=3802
{
val $u: reflect.runtime.universe.type = scala.reflect.runtime.`package`.universe;
val $m: $u.Mirror = scala.reflect.runtime.`package`.universe.runtimeMirror(this.getClass().getClassLoader());
$u.TypeTag.apply[db.Raw]($m, {
final class $typecreator2 extends TypeCreator {
def <init>(): $typecreator2 = {
$typecreator2.super.<init>();
()
};
def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
val $u: U = $m$untyped.universe;
val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
$m.staticClass("db.Raw").asType.toTypeConstructor
}
};
new $typecreator2()
})
}
Block(List(ValDef(Modifiers(), TermName("$u"), TypeTree().setOriginal(SingletonTypeTree(Select(Select(Select(Select(Ident(scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), TermName("universe")))), Select(Select(Select(Select(Ident(scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), TermName("universe"))), ValDef(Modifiers(), TermName("$m"), TypeTree().setOriginal(Select(Ident(TermName("$u")), TypeName("Mirror"))), Apply(Select(Select(Select(Select(Select(Ident(scala), scala.reflect), scala.reflect.runtime), scala.reflect.runtime.package), TermName("universe")), TermName("runtimeMirror")), List(Apply(Select(Apply(Select(This(TypeName("DMarcReportReader")), TermName("getClass")), List()), TermName("getClassLoader")), List()))))), Apply(TypeApply(Select(Select(Ident(TermName("$u")), TermName("TypeTag")), TermName("apply")), List(TypeTree())), List(Ident(TermName("$m")), Block(List(ClassDef(Modifiers(FINAL), TypeName("$typecreator2"), List(), Template(List(Ident(scala.reflect.api.TypeCreator)), noSelfType, List(DefDef(Modifiers(), termNames.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(Apply(Select(Super(This(TypeName("$typecreator2")), typeNames.EMPTY), termNames.CONSTRUCTOR), List())), Literal(Constant(())))), DefDef(Modifiers(), TermName("apply"), List(TypeDef(Modifiers(PARAM), TypeName("U"), List(), TypeTree().setOriginal(TypeBoundsTree(TypeTree().setOriginal(Ident(scala.Nothing)), TypeTree().setOriginal(CompoundTypeTree(Template(List(Ident(scala.reflect.api.Universe), Ident(scala.Singleton)), noSelfType, List()))))))), List(List(ValDef(Modifiers(PARAM), TermName("$m$untyped"), TypeTree().setOriginal(AppliedTypeTree(Ident(scala.reflect.api.Mirror), List(TypeTree().setOriginal(Ident(TypeName("U")))))), EmptyTree))), TypeTree().setOriginal(SelectFromTypeTree(TypeTree().setOriginal(Ident(TypeName("U"))), TypeName("Type"))), Block(List(ValDef(Modifiers(), TermName("$u"), TypeTree().setOriginal(Ident(TypeName("U"))), Select(Ident(TermName("$m$untyped")), TermName("universe"))), ValDef(Modifiers(), TermName("$m"), TypeTree().setOriginal(Select(Ident(TermName("$u")), TypeName("Mirror"))), TypeApply(Select(Ident(TermName("$m$untyped")), TermName("asInstanceOf")), List(TypeTree().setOriginal(Select(Ident(TermName("$u")), TypeName("Mirror"))))))), Select(Select(Apply(Select(Ident(TermName("$m")), TermName("staticClass")), List(Literal(Constant("db.Raw")))), TermName("asType")), TermName("toTypeConstructor")))))))), Apply(Select(New(Ident(TypeName("$typecreator2"))), termNames.CONSTRUCTOR), List())))))
performing macro expansion slick.driver.PostgresDriver.api.TableQuery.apply[db.Reports] at source-/scalaproject/src/main/scala/db/package.scala,line-4,offset=88
TableQuery.apply[db.Reports](((tag: Tag) => new db.Reports(tag)))
Apply(TypeApply(Select(Ident(slick.lifted.TableQuery), TermName("apply")), List(TypeTree())), List(Function(List(ValDef(Modifiers(PARAM), TermName("tag"), Ident(slick.lifted.Tag), EmptyTree)), Apply(Select(New(TypeTree()), termNames.CONSTRUCTOR), List(Ident(TermName("tag")))))))
performing macro expansion slick.driver.PostgresDriver.api.TableQuery.apply[db.Records] at source-/scalaproject/src/main/scala/db/package.scala,line-6,offset=154
TableQuery.apply[db.Records](((tag: Tag) => new db.Records(tag)))
Apply(TypeApply(Select(Ident(slick.lifted.TableQuery), TermName("apply")), List(TypeTree())), List(Function(List(ValDef(Modifiers(PARAM), TermName("tag"), Ident(slick.lifted.Tag), EmptyTree)), Apply(Select(New(TypeTree()), termNames.CONSTRUCTOR), List(Ident(TermName("tag")))))))
performing macro expansion `package`.this.materializeClassTag[db.Record]() at source-/scalaproject/src/main/scala/db/Reports.scala,line-69,offset=2078
ClassTag.apply[db.Record](classOf[db.Record])
Apply(TypeApply(Select(Ident(scala.reflect.ClassTag), TermName("apply")), List(TypeTree())), List(Literal(Constant(db.Record))))
performing macro expansion slick.driver.PostgresDriver.api.TableQuery.apply[db.Raws] at source-/scalaproject/src/main/scala/db/package.scala,line-5,offset=121
TableQuery.apply[db.Raws](((tag: Tag) => new db.Raws(tag)))
Apply(TypeApply(Select(Ident(slick.lifted.TableQuery), TermName("apply")), List(TypeTree())), List(Function(List(ValDef(Modifiers(PARAM), TermName("tag"), Ident(slick.lifted.Tag), EmptyTree)), Apply(Select(New(TypeTree()), termNames.CONSTRUCTOR), List(Ident(TermName("tag")))))))
performing macro expansion `package`.this.materializeClassTag[db.Report]() at source-/scalaproject/src/main/scala/db/Reports.scala,line-82,offset=2550
ClassTag.apply[db.Report](classOf[db.Report])
Apply(TypeApply(Select(Ident(scala.reflect.ClassTag), TermName("apply")), List(TypeTree())), List(Literal(Constant(db.Report))))
performing macro expansion `package`.this.materializeClassTag[db.Raw]() at source-/scalaproject/src/main/scala/db/Reports.scala,line-90,offset=2803
ClassTag.apply[db.Raw](classOf[db.Raw])
Apply(TypeApply(Select(Ident(scala.reflect.ClassTag), TermName("apply")), List(TypeTree())), List(Literal(Constant(db.Raw))))
[error] one error found
[error] (compile:compile) Compilation failed
[error] Total time: 1 s, completed Sep 14, 2015 3:08:59 PM
任何想法如何解决？