问题
I'm looking at Scala traits, but have yet to program in it, making this a hypothetical question.
All of the examples that I've seen so far have concrete or abstract fields that only use val in their declaration instead of var. Can fields declared with var be used in Scala traits?
TIA, Matthew
回答1:
If you try it you'll see it works:
scala> trait TestTrait {
| var x = 1
| }
defined trait TestTrait
scala> val t = new TestTrait { }
t: TestTrait = $anon$1@4c32060c
scala> t.x = 2
t.x: Int = 2
scala> t.x
res0: Int = 2
If you read into how var and val are compiled in Scala this makes sense. A val is a private field with an auto-generated getter method, and the only difference for a var is that is has a setter as well.
来源：https://stackoverflow.com/questions/18539829/can-scala-traits-have-vars-not-just-vals