Question

我正在尝试编写一个简单的宏注释，让我每次都可以对方法执行进行计时 - 如果我注释方法定义 - 或者只是一次注释方法调用。

注释方法定义可以正常工作。然而

object Main {
  def main(args:Array[String]): Unit ={
    @MyMacro
    doTest() //"Hello World"
  }
}

在语法上似乎不正确。因为intellij抱怨说:Unit ={之后它会预期＆＃34;一个}，当我删除@MyMacro时，警告会消失。

注释方法调用（或者任意表达式）的正确方法是什么？

（例如，我可能没有兴趣为getX的所有来电获取时间，但我可能想要在代码中的某个特定位置测量花费的时间：

val x = @MyMacro getX()

）

更新

这有效：

object Main {
  def main(args:Array[String]): Unit ={
    hello()
  }

  @MyMacro
  def hello(): Unit ={
    println("Hello World")
  }
}

这不会编译：

object Main {
  def main(args:Array[String]): Unit ={
    hello(): @MyMacro
  }

  def hello(): Unit ={
    println("Hello World")
  }
}

，因为

Error:(10, 15) macro annotation could not be expanded (the most common reason for that is that you need to enable the macro paradise plugin; another possibility is that you try to use macro annotation in the same compilation run that defines it)
hello(): @MyMacro
          ^

我只是使用

编译sbt

object BuildSettings {
  val buildSettings = Defaults.defaultSettings ++ Seq(
    version := "0.0.1",
    scalaVersion := "2.11.8",
    scalacOptions += "",
    crossScalaVersions := Seq("2.10.2", "2.10.3", "2.10.4", "2.10.5", "2.10.6", "2.11.0", "2.11.1", "2.11.2", "2.11.3", "2.11.4", "2.11.5", "2.11.6", "2.11.7", "2.11.8"),
    resolvers += Resolver.sonatypeRepo("releases"),
    addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)
  )
}

object ScalaMacroDebugBuild extends Build {
  import BuildSettings._

  lazy val root: Project = Project(
    "root",
    file("."),
    settings = buildSettings
  ) aggregate(macros, examples)

  lazy val macros: Project = Project(
    "macros",
    file("macros"),
    settings = buildSettings ++ Seq(
      libraryDependencies <+= (scalaVersion)("org.scala-lang" % "scala-compiler" % _))
  )

  lazy val examples: Project = Project(
    "examples",
    file("examples"),
    settings = buildSettings
  ) dependsOn(macros)
}

哪个应该处理这两个问题？

Answer 1

An annotation of an expression e appears after the expression e, separated by a colon.

所以val x = getX(): @MyMacro应该有用。

Scala - 宏注释方法调用？

1 个答案: