是否可以提供從Iterable [T]到Iterable [U]的隱式轉換？

Question

鑑於一些情況下類Foo(x: Int)和Bar(x: Int)，一個（隱含的）功能f1即轉換Foo => Bar是有可能實現以下目標：

val foos: List[Foo] = List(Foo(1), Foo(2)) 
def myFunction(bar: List[Bar]) = ??? 

myFunction(foos) // Here foos should be implicitly converted from List[Foo] to List[Bar] 

Answer 1

也許這樣的事情是你在找什麼？

scala> case class Foo(x: Int) {} 
defined class Foo 

scala> case class Bar(y: Int) {} 
defined class Bar 

scala> import scala.language.implicitConversions 
import scala.language.implicitConversions 

scala> implicit def f2b(foos: List[Foo]): List[Bar] = foos.map(foo => new Bar(foo.x)) 
f2b: (foos: List[Foo])List[Bar] 

scala> def barIt(bs: List[Bar]): Unit = bs.foreach(bar => println(bar.y)) 
barIt: (bs: List[Bar])Unit 

scala> val foos = List(new Foo(59), new Foo(2), new Foo(99)) 
foos: List[Foo] = List(Foo(59), Foo(2), Foo(99)) 

scala> barIt(foos) 
59 
2 
99 

Answer 2

鑑於從Foo到Bar隱式轉換，下面將給出列表一個簡單的隱式轉換：

implicit def foos2bars(foos: List[Foo]): List[Bar] = foos.map(f => f:Bar)