[英]How do I write this without using a Try/Catch block?
I am looking to rewrite this scala function, but I am new to the language, I understand there is a alternative to using try\\catch blocks. 我希望重写此scala函数,但是我是该语言的新手,我知道可以使用try \\ catch块来替代。 How would you guys rewrite this function?
你们将如何重写此功能?
def updateStationPost = Action { implicit request =>
StationForm.bindFromRequest.fold(
errors => { //needs to be revised!!
BadRequest(html.updateStation(errors,
Station(
request.body.asFormUrlEncoded.get("id")(0).toLong,
request.body.asFormUrlEncoded.get("operator")(0).toLong,
request.body.asFormUrlEncoded.get("name")(0),
try {
request.body.asFormUrlEncoded.get("number")(0).toInt
} catch {
case e:Exception => { 0 } //this exception happens when trying to convert the number when there is nothing in the flash scope to convert.
},
request.body.asFormUrlEncoded.get("timezone")(0)
),
Operators.retrieveJustOperators() //ugh... needs to be revised..
)
)
},
{ case(stationFormObj) =>
Stations.update(stationFormObj)
Redirect(routes.StationsController.index)
}
)
}
A general way of managing this is to use Try to wrap code that could throw an exception. 管理此问题的一般方法是使用“ 尝试包装”可能引发异常的代码。 Some of the ways of using this are illustrated below:
使用它的一些方法如下所示:
def unpredictable() = {
Try(Console.readLine("Int please: ").toInt) getOrElse 0
}
If the console read does not contain a parseable integer, then it throws an exception. 如果控制台读取的内容不包含可解析的整数,则它将引发异常。 This code just returns a 0 if there was an error, but you could put other statements there.
如果发生错误,此代码仅返回0,但是您可以在其中放置其他语句。 As an alternative, you could use pattern matching to handle the situation.
或者,您可以使用模式匹配来处理这种情况。
def unpredictable() = {
Try(Console.readLine("Int please: ").toInt) match {
case Success(i) => i
case Failure(e) => println(e.getMessage())
}
}
You can also just return a Try and let the caller decide how to handle the failure. 您也可以只返回Try,让调用者决定如何处理失败。
How about: 怎么样:
import scala.util.control.Exception.handling
// Create a val like this as you reuse it over and over
val form: Option[Map[String, Seq[String]]] = request.body.asFormUrlEncoded
// Create some helper functions like this
val nfeHandler = handling(classOf[NumberFormatException]) by (_ => 0)
val intNFEHandler = (str: String) => nfeHandler apply str.toInt
val longNFEHandler = (str: String) => nfeHandler apply str.toLong
// You can use this instead of your try catch.. but this is just a sugar.. perhaps cleaner
intNFEHandler apply form.get("id")(0)
Here if the form was something like: Option(Map("id" -> Seq.empty[String]))
这里的形式是这样的:
Option(Map("id" -> Seq.empty[String]))
form.get("id")(0)
would blow up with java.lang.IndexOutOfBoundsException. form.get("id")(0)
会因java.lang.IndexOutOfBoundsException而form.get("id")(0)
。
I would suggest to have another helper: 我建议再找一个助手:
// takes fieldNames and returns Option(fieldValue)
val fieldValueOpt = (fieldName: String) => form.flatMap(_.get(fieldName).flatMap(_.headOption))
Then create a validate method which performs pattern matching on all the fieldValue optionals, extract the values and create your Station object. 然后创建一个validate方法,该方法对所有fieldValue可选参数执行模式匹配,提取值并创建Station对象。
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