Scala 不返回字段的注释 [英] Scala returns no annotations for a field

问题描述

我有这个:

class Max(val value : Int) extends StaticAnnotation{}

class Child() extends Parent {
  @Max(5) val myMember= register("myMember")
}

abstract class Parent {
     def register(fieldName : String) = {
             val cls = getClass
             import scala.reflect.runtime.universe._
             val mirror = runtimeMirror(cls.getClassLoader)
             val clsSymbol = mirror.staticClass(cls.getCanonicalName)
             val fieldSymbol = clsSymbol.typeSignature.member(TermName(fieldName))
             println(s"${fieldSymbol.fullName}   " + fieldSymbol.annotations.size)
     }
}

这不起作用，不知何故，它返回 0 个注释，如果相反，我将注释放在类上，那么我可以很好地阅读它.为什么?

this does not work, somehow, it returns 0 annotations, if instead, I put the annotation on the class, then I can read it fine. Why?

推荐答案

发现上一行:

clsSymbol.typeSignature.member(TermName(fieldName))

为val"(当然没有任何注释)返回自动生成的 getter 的符号，而不是 val 本身的符号.如果我这样做:

was returning the symbol of the auto generated getter for the "val" (which of course does not have any annotation), instead of the symbol from the val itself. If instead I do:

clsSymbol.toType.decl(TermName(s"${fieldName} "))

这似乎工作正常.出于我不知道的任何原因，如果我在 TermName 的末尾写一个空格，那么它会返回带有注释的字段符号.

that seems to work fine. For any reason that I do not know, if I write a space at the end of the TermName, then it returns the field symbol with the annotations.

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