Scala if else 枚举赋值运算符失败

Question

我有以下 Scala 代码：

// RunMode.scala
object RunMode extends Enumeration {
  val CLIENT_MODE = Value("CLIENT")
  val SERVER_MODE = Value("SERVER")
}

// Driver.scala
object MyApp extends App {
  // Don't worry about this too much, the point is we get a valid
  // instance of RunMode to work with
  val runMode : RunMode = getRunMode(args)

  val qualifier : String = if runMode.eq(RunMode.CLIENT_MODE) "whistle" else "feather"

  // rest of main omitted for brevity
}

运行时，我在三元运算符上收到以下编译器错误：

/Users/myuser/myapp/src/main/com/me/myapp/Driver.scala:22: '(' expected but identifier found.
  val qualifier : String = if runMode.eq(RunMode.CLIENT_MODE) "whistle" else "feather"

显然，所需的行为可以重写为：

var qualifier : String = null
if(runMode.eq(RunMode.CLIENT_MODE)) {
  qualifier = "whistle"
} else {
  qualifier = "feather"
}

但为什么会出现此错误？解决方法是什么？

Answer 1

Scala 中没有三元运算符。使用 if-else:

val qualifier : String = if (runMode eq RunMode.CLIENT_MODE) "whistle" else "feather"

Scala if else 枚举赋值运算符失败

Scala if else assignment operator with enum is failing

string

scala

ternary-operator