Scala 中泛型类型的模式匹配
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Pattern matching on generic type in Scala
提问by Core_Dumped
I have scala function that looks like this:
我有如下所示的 Scala 函数：
Now, depending upon the type of T (In my case, it can be Double, Booleanand LocalDate),
I need to apply functions on ob. Something like this (I know the code will make no sense but I am trying to convey what I mean to do):
现在，根据 T 的类型（在我的情况下，它可以是Double,Boolean和LocalDate），我需要在 上应用函数ob。像这样的东西（我知道代码没有意义，但我试图传达我的意思）：
def X[T](ob: Observable[T]): Observable[T] = {
//code
T match {
case Double => DoSomething1(ob:Observable[Double]):Observable[Double]
case Boolean => DoSomething2(ob:Observable[Boolean]):Observable[Boolean]
case LocalDate => DoSomething3(ob:Observable[LocalDate]):Observable[LocalDate]
}
}
Taking into consideration the Erasure property of Scala, can reflection be somehow used to get the job done? Is it even possible?
考虑到 Scala 的 Erasure 属性，可以以某种方式使用反射来完成工作吗？甚至有可能吗？
回答by om-nom-nom
I would go with TypeTag if you're on 2.10+
如果您使用的是 2.10+，我会选择 TypeTag
import reflect.runtime.universe._
class Observable[Foo]
def X[T: TypeTag](ob: Observable[T]) = ob match {
case x if typeOf[T] <:< typeOf[Double] => println("Double obs")
case x if typeOf[T] <:< typeOf[Boolean] => println("Boolean obs")
case x if typeOf[T] <:< typeOf[Int] => println("Int obs")
}
X(new Observable[Int])
// Int obs
See also this lengthy, but awesome answer
另请参阅这个冗长但很棒的答案
Note also that I only took a glimpse at scala reflection, so likely somebody may write a better example of TypeTag usage.
另请注意，我只瞥了一眼 scala 反射，因此可能有人会编写一个更好的 TypeTag 用法示例。
