如何避免Scala中的可变局部变量? [英] How to avoid mutable local variables in Scala?

问题描述

最好避免在Scala中使用可变变量.

It is considered a good practice to avoid using mutable variables in Scala.

摘自"Scala编程，第二版"，第52页:"Scala允许您以命令式风格进行编程，但鼓励您采用更具功能性的风格"，后来又"Scala鼓励您倾向于val，但最终可以根据手头的工作找到最好的工具."

From "Programming in Scala, 2nd Edition", page 52: "Scala allows you to program in an imperative style, but encourages you to adopt a more functional style" and later "Scala encourages you to lean towards vals, but ultimately reach for the best tool given the job at hand."

您如何在Scala中使此命令结构优雅(关注变量 count ):

How do you make this imperative construct elegant in Scala (focusing on variable count):

var count = 0
val foo  = getRequest()
if(foo.isJsonObject){
  count = doSomething(foo)
}
if(count>0){
  specialCall()
} else{
  defaultCall()
}

您使用什么构造或模式将命令式样式的代码转换为功能样式? 您是否使用Option类或其他一些构造?

What construct or pattern do you use to transform your code with an imperative style to a functional style? Do you make use of the Option class or some other constructs?

推荐答案

不确定您是否提供了足够的上下文，但怎么办:

Not sure if you are giving enough context, but what about:

val foo  = getRequest()
val count = if (foo.isJsonObject) doSomething(foo) else 0
if (count > 0) {
  specialCall()
} else {
  defaultCall()
}

通常，一般来说，Scala API(集合，Option，Try，Future等)及其操作(map，flatMap，filter，fold等)都允许您可以非常简洁地表达最必要的结构.

Normally, the Scala API in general (collections, Option, Try, Future, etc) and their operations (map, flatMap, filter, fold, etc) allow you to express most imperative constructs quite concisely.

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