使用 scala.util.control.Exception [英] Using scala.util.control.Exception

问题描述

有没有人有使用 scala.util.control.Exception 版本 2.12.0 (2.8.0 版), ?我正在努力从类型中弄清楚.

Does anybody have good examples of using scala.util.control.Exception version 2.12.0 (version 2.8.0), ? I am struggling to figure it out from the types.

推荐答案

确实 - 我也觉得这很令人困惑！这是一个问题，我有一些属性可能是可解析的日期:

Indeed - I also find it pretty confusing! Here's a problem where I have some property which may be a parseable date:

def parse(s: String) : Date = new SimpleDateFormat("yyyy-MM-dd").parse(s)
def parseDate = parse(System.getProperty("foo.bar"))

type PE = ParseException
import scala.util.control.Exception._

val d1 = try { 
             parseDate
           } catch { 
             case e: PE => new Date
           }

将其转换为函数形式:

val date =
     catching(classOf[PE]) either parseDate fold (_ => new Date, identity(_) ) 

在上面的代码中，把catch(t)或者expr变成一个Either[T, E]，其中T是throwable 的类型和 E 是表达式的类型.然后可以通过 fold 将其转换为特定值.

In the above code, turns catching(t) either expr will result in an Either[T, E] where T is the throwable's type and E is the expression's type. This can then be converted to a specific value via a fold.

或者另一个版本:

val date =
     handling(classOf[PE]) by (_ => new Date) apply parseDate

这可能更清楚一些 - 以下是等效的:

This is perhaps a little clearer - the following are equivalent:

handling(t) by g apply f 
try { f } catch { case _ : t => g }

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