在Scala中泛型类型的模式匹配 [英] Pattern matching on generic type in Scala
问题描述
现在,根据T的类型(在我的情况下,它可以是 Double
,布尔值
和 LocalDate
),
我需要在 OB
。像这样的东西(我知道代码没有意义,但我想传达我的意思):
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]
}
}
考虑到Scala的擦除属性,反射可以以某种方式用来完成工作吗?它甚至有可能吗?
如果您使用2.10以上版本,我会使用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
另请参阅这个冗长但很棒的答案
还要注意,我只是瞥了一眼scala反射,所以有人可能会写一个更好的TypeTag使用示例。
I have scala function that looks like this:
Now, depending upon the type of T (In my case, it can be Double
, Boolean
and 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):
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?
I would go with TypeTag if you're on 2.10+
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
Note also that I only took a glimpse at scala reflection, so likely somebody may write a better example of TypeTag usage.
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