Scala

Question

我有这个代码：

def +(s: String) = s.headOption

val foo = +("hello")

尝试编译时，出现编译错误：

Error: value unary_+ is not a member of String
    val foo = +("hello")

如何防止编译器插入对 String.unary_- 的调用，而是在范围内调用该方法？

Answer 1

val foo = this.+("hello") //this will call the class, object etc. and you will get the correct reference for the method :)

或者：

import <path>._

val foo = classname.+("hello")

或者：

import <path>.<class>

val foo = <class>.+("hello")

例如：

package test

object SO {

  def +(s:String) = s.headOption

}

package test

object add extends App {
  import test.SO

  println(SO.+("hello"))
}

回复：

Some(h)

Ex2:

package test

class SO {}
object SO {
    def apply(): SO = {
        new SO
    }
    def +(s:String) = s.headOption
}



package test

object add extends App {
  import test.SO

  println(SO.+("string"))
}

回复：

 Some(s)

Scala - 如何不调用一元方法

Scala - how to not call a unary method

methods

unary-operator