Symbol 是一个案例对象吗?
Is the Symbol a case object?
{ sealed trait Sealed; case object Foo extends Sealed; case class Bar(s: String) extends Sealed; trait Baz extends Sealed }
import scala.reflect.runtime.universe._
val List(bar, baz, foo) = symbolOf[Sealed].asClass.knownDirectSubclasses.toList
我试过.asClass.primaryConstructor.isStatic
,但如果将密封特征定义为依赖类型,那将不起作用。
Symbol#isModuleClass
貌似可以判断符号是不是object
,foo.asClass.isClass
可以判断是否有大小写修饰符。请注意,如果您在其他类型的符号(方法、术语等)上使用它,asClass
将抛出异常。
对象测试:
scala> bar.isModuleClass // case class
res28: Boolean = false
scala> baz.isModuleClass // trait
res29: Boolean = false
scala> foo.isModuleClass // case object
res30: Boolean = true
对于其他类型:
scala> val a = ""
a: String = ""
scala> symbolOf[a.type].isModuleClass
res34: Boolean = false
case class A(value: String) ; object A { def default = A("") }
scala> symbolOf[A].isModuleClass
res35: Boolean = false
scala> symbolOf[A.type].isModuleClass
res36: Boolean = true
根据 API 文档和 SI-6012 它 似乎 像 isModule
也应该有效,但它只 returns companionSymbol.
为真
案例测试:
scala> bar.asClass.isCaseClass // case class
res44: Boolean = true
scala> baz.asClass.isCaseClass // trait
res45: Boolean = false
scala> foo.asClass.isCaseClass // case object
res46: Boolean = true
对于其他类型(定义与上述示例相同):
scala> symbolOf[a.type].asClass.isCaseClass // plain singleton object
res47: Boolean = false
scala> symbolOf[A].asClass.isCaseClass // case class
res48: Boolean = true
scala> symbolOf[A.type].asClass.isCaseClass // non-case object
res49: Boolean = false
放在一起:
def isCaseObject(symbol: Symbol): Boolean =
symbol.isModuleClass && symbol.asClass.isCaseClass
scala> isCaseObject(bar)
res50: Boolean = false
scala> isCaseObject(baz)
res51: Boolean = false
scala> isCaseObject(foo)
res52: Boolean = true
scala> isCaseObject(symbolOf[a.type])
res53: Boolean = false
scala> isCaseObject(symbolOf[A])
res54: Boolean = false
scala> isCaseObject(symbolOf[A.type])
res55: Boolean = false
{ sealed trait Sealed; case object Foo extends Sealed; case class Bar(s: String) extends Sealed; trait Baz extends Sealed }
import scala.reflect.runtime.universe._
val List(bar, baz, foo) = symbolOf[Sealed].asClass.knownDirectSubclasses.toList
我试过.asClass.primaryConstructor.isStatic
,但如果将密封特征定义为依赖类型,那将不起作用。
Symbol#isModuleClass
貌似可以判断符号是不是object
,foo.asClass.isClass
可以判断是否有大小写修饰符。请注意,如果您在其他类型的符号(方法、术语等)上使用它,asClass
将抛出异常。
对象测试:
scala> bar.isModuleClass // case class
res28: Boolean = false
scala> baz.isModuleClass // trait
res29: Boolean = false
scala> foo.isModuleClass // case object
res30: Boolean = true
对于其他类型:
scala> val a = ""
a: String = ""
scala> symbolOf[a.type].isModuleClass
res34: Boolean = false
case class A(value: String) ; object A { def default = A("") }
scala> symbolOf[A].isModuleClass
res35: Boolean = false
scala> symbolOf[A.type].isModuleClass
res36: Boolean = true
根据 API 文档和 SI-6012 它 似乎 像 isModule
也应该有效,但它只 returns companionSymbol.
案例测试:
scala> bar.asClass.isCaseClass // case class
res44: Boolean = true
scala> baz.asClass.isCaseClass // trait
res45: Boolean = false
scala> foo.asClass.isCaseClass // case object
res46: Boolean = true
对于其他类型(定义与上述示例相同):
scala> symbolOf[a.type].asClass.isCaseClass // plain singleton object
res47: Boolean = false
scala> symbolOf[A].asClass.isCaseClass // case class
res48: Boolean = true
scala> symbolOf[A.type].asClass.isCaseClass // non-case object
res49: Boolean = false
放在一起:
def isCaseObject(symbol: Symbol): Boolean =
symbol.isModuleClass && symbol.asClass.isCaseClass
scala> isCaseObject(bar)
res50: Boolean = false
scala> isCaseObject(baz)
res51: Boolean = false
scala> isCaseObject(foo)
res52: Boolean = true
scala> isCaseObject(symbolOf[a.type])
res53: Boolean = false
scala> isCaseObject(symbolOf[A])
res54: Boolean = false
scala> isCaseObject(symbolOf[A.type])
res55: Boolean = false