Scala/Lift检查日期格式是否正确 [英] Scala/Lift check if date is correctly formatted

问题描述

我的电梯应用程序中有一个日期输入框，我想检查用户输入的日期格式是否正确: dd/mm/yyyy .

I have a date input box in my lift application, and I want to check that a user-entered date is in correct format: dd/mm/yyyy.

如何在Scala中为此编写正则表达式检查?我看过模式匹配示例-但这似乎太复杂了.

How can I write a regex check for this in scala? I've looked at pattern matching examples - but that seems over-complicated.

PS:我不必使用正则表达式，欢迎使用其他任何替代方法！

PS: I don't have to use regex, any other alternatives are welcome!

推荐答案

SimpleDateFormat丑陋且(更令人不安的)非线程安全的.如果您尝试同时在2个或更多线程中使用同一实例，则可能会以最不愉快的方式崩溃.

SimpleDateFormat is ugly and (more disturbingly) non-thread-safe. If you try to simultaneously use the same instance in 2 or more threads then expect things to blow up in a most unpleasant fashion.

JodaTime更好:

JodaTime is far nicer:

import org.joda.time.format._
val fmt = DateTimeFormat forPattern "dd/MM/yyyy"
val input = "12/05/2009"
val output = fmt parseDateTime input

如果抛出IllegalArgumentException，则日期无效.

If it throws an IllegalArgumentException, then the date wasn't valid.

由于我怀疑您想知道实际日期是否有效，因此您可能想返回Option[DateTime]，如果它无效则返回None.

As I suspect you'll want to know the actual date if it was valid, you may want to return an Option[DateTime], with None if it was invalid.

def parseDate(input: String) = try {
  Some(fmt parseDateTime input)
} catch {
  case e: IllegalArgumentException => None
}

或者，如果无法格式化，请使用Either捕获实际的异常:

Alternatively, use an Either to capture the actual exception if formatting wasn't possible:

def parseDate(input: String) = try {
  Right(fmt parseDateTime input)
} catch {
  case e: IllegalArgumentException => Left(e)
}

更新

要使用Either，您有两种主要策略:

To then use the Either, you have two main tactics:

映射两侧之一:

parseDate(input).left map (_.getMessage)
//will convert the Either[IllegalArgumentException, DateTime]
//to an Either[String, DateTime]

折叠:

parseDate(input) fold (
  _ => S.error(
    "birthdate",
    "Invalid date. Please enter date in the form dd/mm/yyyy."),
  dt => successFunc(dt)
)

当然，两者可以组成:

parseDate(input).left map (_.getMessage) fold (
  errMsg => S.error("birthdate", errMsg), //if failure (Left by convention)
  dt => successFunc(dt) //if success (Right by convention)
)

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