问题描述
解析日期时遇到一些问题。我有一系列支持的格式，一旦我从API收到日期（字符串），我尝试解析它迭代格式，直到我得到一个有效的NSDate对象。
Having some problems parsing date. I have an array of supported formats and once I receive the date (string) from API, I try to parse it iterating through the formats until I get a valid NSDate object.
来自Xcode Playground的片段 -
A snippet from Xcode Playground --
let dateString = "02/06/1987" // --> want to parse into this Feb 6, not Jun 2
let dateFormatIncorrect = "dd.MM.yyyy"
let dateFormatCorrect = "MM/dd/yyyy"
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = dateFormatIncorrect
let date = dateFormatter.dateFromString(dateString)! // "Jun 2, 1987, 12:00 AM"
dateFormatter.dateFormat = dateFormatCorrect
let date2 = dateFormatter.dateFromString(dateString)! // "Feb 6, 1987, 12:00 AM"
为什么它会解析日期，即使对于给定的字符串，格式显然不正确？无法在文档中找到有关日期格式化程序忽略分隔符的任何内容。
Why does it parse the date even though the format is clearly incorrect for a given string? Could not find anything in the docs regarding date formatter ignoring separators.
我意识到正确的解决方案是从API返回固定格式但是想知道这里发生了什么？
I realise the proper solution would be to have a fixed format returned from API but was wondering what is happening here?
谢谢。
推荐答案
似乎<$ c $当解析日期字符串时，c> NSDateFormatter 非常宽松。
不幸的是，我找不到这方面的参考，但即使有
It seems that NSDateFormatter is extremely lenient when parsing a date string.Unfortunately, I could not find a reference for this, but even with
dateFormatIncorrect = "'aaa'dd'bbb'MM'ccc'yyyy'ddd'"
日期字符串02/06/1987已成功解析。有一个 lenient 属性，
但默认情况下是 false ，并明确设置它没有区别。
the date string "02/06/1987" is successfully parsed. There is a lenient property,but that is false by default, and setting it explicitly makes no difference.
作为解决方法，您可以将解析后的日期转换回字符串，并且仅当
结果等于原始字符串，接受日期：
As a workaround, you could convert the parsed date back to a string, and only ifthe result is equal to the original string, the date is accepted:
extension NSDateFormatter {
func checkedDateFromString(string : String) -> NSDate? {
if let date = self.dateFromString(string) {
if self.stringFromDate(date) == string {
return date
}
}
return nil
}
}
使用此自定义扩展程序
dateFormatter.checkedDateFromString(dateString)
对于错误的日期格式返回 nil 。
returns nil for the incorrect date format.
通常，如果使用固定日期格式，还应将区域设置
设置为en_US_POSIX
Generally, if you work with fixed date formats, you should also set the localeto "en_US_POSIX"
dateFormatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")
（参见）。但是，这对于这个
特定问题没有区别。
(see What is the best way to deal with the NSDateFormatter locale "feechur"?). However, this makes no difference for thisparticular problem.
Swift 3更新：
extension DateFormatter {
func checkedDate(from: String) -> Date? {
if let date = date(from: from), string(from: date) == from {
return date
}
return nil
}
}
这篇关于NSDateFormatter仍在解析而不是格式不正确的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！