使用scala.util.control.Exception
有人有使用()的好例子吗?我正努力从这些类型中找出答案 的确如此——我也觉得这很令人困惑!这里有一个问题,我有一些属性可能是可解析的日期:使用scala.util.control.Exception,scala,scala-2.8,Scala,Scala 2.8,有人有使用()的好例子吗?我正努力从这些类型中找出答案 的确如此——我也觉得这很令人困惑!这里有一个问题,我有一些属性可能是可解析的日期: 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.E
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
}
将其切换为功能形式:
val date =
catching(classOf[PE]) either parseDate fold (_ => new Date, identity(_) )
在上面的代码中,旋转捕捉(t)或expr
将导致或[t,E]
其中t
是可丢弃的类型,E
是表达式的类型。然后可以通过折叠将其转换为特定值
或另一个版本:
val date =
handling(classOf[PE]) by (_ => new Date) apply parseDate
这也许更清楚一点——以下是等效的:
handling(t) by g apply f
try { f } catch { case _ : t => g }
以下是一些例子:
编译器/scala/tools/nsc/InteractiveReader.scala
def readLine(prompt: String): String = {
def handler: Catcher[String] = {
case e: IOException if restartSystemCall(e) => readLine(prompt)
}
catching(handler) { readOneLine(prompt) }
}
编译器/scala/tools/nsc/Interpreter.scala
/** We turn off the binding to accomodate ticket #2817 */
def onErr: Catcher[(String, Boolean)] = {
case t: Throwable if bindLastException =>
withoutBindingLastException {
quietBind("lastException", "java.lang.Throwable", t)
(stringFromWriter(t.printStackTrace(_)), false)
}
}
catching(onErr) {
unwrapping(wrapperExceptions: _*) {
(resultValMethod.invoke(loadedResultObject).toString, true)
}
}
...
/** Temporarily be quiet */
def beQuietDuring[T](operation: => T): T = {
val wasPrinting = printResults
ultimately(printResults = wasPrinting) {
printResults = false
operation
}
}
/** whether to bind the lastException variable */
private var bindLastException = true
/** Temporarily stop binding lastException */
def withoutBindingLastException[T](operation: => T): T = {
val wasBinding = bindLastException
ultimately(bindLastException = wasBinding) {
bindLastException = false
operation
}
}
编译器/scala/tools/nsc/io/Process.scala
def exitValue(): Option[Int] =
catching(classOf[IllegalThreadStateException]) opt process.exitValue()
library/scala/xml/include/sax/Main.scala
def saxe[T](body: => T) = catching[T](classOf[SAXException]) opt body
...
ignoring(classOf[SAXException]) {
includer.setProperty(lexicalHandler, s)
s setFilter includer
}
还有一种选择:failAsValue(classOf[PE])(新日期){parseDate}
:)你能详细介绍一下“捕获…展开”的例子吗?