代码之家 › 专栏 › 技术社区 › Raj Pawan Gumdal

NSDateFormatter在iOS 3.0中为@“dd-MM-yy”返回nil

nsdateformatter nsdate ios4 iphone-sdk-3.0 cocoa-touch

Raj Pawan Gumdal · 技术社区 · 14 年前

NSDate *date =nil;
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
[dateFormatter setDateFormat:@"dd-MM-yy"];
date = [dateFormatter dateFromString:inString];
[dateFormatter release];

它工作得非常好,正如iOS 4.0所期望的那样。但3.0中没有相同的代码。

我得到的字符串类似于“12-Nov-10”,它包含在in string指针中。

谢谢,

拉吉

编辑: 在Harkonian和Q&A讨论提出以下建议后,制定适当的准则:

NSDate *date =nil;
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
[dateFormatter setDateFormat:@"dd-MMM-yy"];

NSLocale *enUSPOSIXLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
[dateFormatter setLocale:enUSPOSIXLocale];
[enUSPOSIXLocale release];

date = [dateFormatter dateFromString:inString];
[dateFormatter release];

2 回复 | 直到 14 年前

memmons 13 年前

如果使用的是用户可见的日期,则应避免设置日期格式字符串,因为很难预测在所有可能的用户配置中如何表示格式字符串。相反,您应该尝试并限制自己设置日期和时间样式(通过-[NSDateFormatter setDateStyle:]和-[NSDateFormatter setTimeStyle:])。

另一方面,如果使用的是固定格式的日期,则应首先将日期格式化程序的区域设置设置为适合固定格式的设置。在大多数情况下,最好选择的语言环境是“en_US_POSIX”,这是一种专门设计的语言环境,无论用户和系统偏好如何,都能产生美式英语结果enòUSòPOSIX“在时间上也是不变的(如果美国在未来某个时候改变了它格式化日期的方式,“enòUS”将改变以反映新的行为,但“enòUSòPOSIX”不会改变),在机器之间(“enòUSòPOSIX”在iPhone操作系统上的工作方式与在Mac OS X上的相同,在其他平台上也一样)。

一旦您将“en_US_POSIX”设置为日期格式化程序的区域设置,您就可以设置日期格式字符串,并且日期格式化程序将为所有用户一致地工作。

上面的信息和更多可以在苹果的 Technical Q&A QA1480

以下是我的应用程序中实现上述建议的代码片段:

static NSDateFormatter* dateFormatter = nil;
if (!dateFormatter) {
   dateFormatter = [[NSDateFormatter alloc] init];

   NSLocale *enUSPOSIXLocale = [[[NSLocale alloc] 
      initWithLocaleIdentifier:@"en_US_POSIX"] autorelease];
   assert(enUSPOSIXLocale != nil);
   [dateFormatter setLocale:enUSPOSIXLocale];
   [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
   dateFormatter.dateFormat = @"EEE, dd MMM yyyy HH:mm:ss +0000";
}

Raj Pawan Gumdal 10 年前

a:  AM/PM
A:  0~86399999 (Millisecond of Day)

c/cc:   1~7 (Day of Week)
ccc:    Sun/Mon/Tue/Wed/Thu/Fri/Sat
cccc:   Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday

d:  1~31 (0 padded Day of Month)
D:  1~366 (0 padded Day of Year)

e:  1~7 (0 padded Day of Week)
E~EEE:  Sun/Mon/Tue/Wed/Thu/Fri/Sat
EEEE:   Sunday/Monday/Tuesday/Wednesday/Thursday/Friday/Saturday

F:  1~5 (0 padded Week of Month, first day of week = Monday)

g:  Julian Day Number (number of days since 4713 BC January 1)
G~GGG:  BC/AD (Era Designator Abbreviated)
GGGG:   Before Christ/Anno Domini

h:  1~12 (0 padded Hour (12hr))
H:  0~23 (0 padded Hour (24hr))

k:  1~24 (0 padded Hour (24hr)
K:  0~11 (0 padded Hour (12hr))

L/LL:   1~12 (0 padded Month)
LLL:    Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec
LLLL:   January/February/March/April/May/June/July/August/September/October/November/December

m:  0~59 (0 padded Minute)
M/MM:   1~12 (0 padded Month)
MMM:    Jan/Feb/Mar/Apr/May/Jun/Jul/Aug/Sep/Oct/Nov/Dec
MMMM:   January/February/March/April/May/June/July/August/September/October/November/December

q/qq:   1~4 (0 padded Quarter)
qqq:    Q1/Q2/Q3/Q4
qqqq:   1st quarter/2nd quarter/3rd quarter/4th quarter
Q/QQ:   1~4 (0 padded Quarter)
QQQ:    Q1/Q2/Q3/Q4
QQQQ:   1st quarter/2nd quarter/3rd quarter/4th quarter

s:  0~59 (0 padded Second)
S:  (rounded Sub-Second)

u:  (0 padded Year)

v~vvv:  (General GMT Timezone Abbreviation)
vvvv:   (General GMT Timezone Name)

w:  1~53 (0 padded Week of Year, 1st day of week = Sunday, NB: 1st week of year starts from the last Sunday of last year)
W:  1~5 (0 padded Week of Month, 1st day of week = Sunday)

y/yyyy: (Full Year)
yy/yyy: (2 Digits Year)
Y/YYYY: (Full Year, starting from the Sunday of the 1st week of year)
YY/YYY: (2 Digits Year, starting from the Sunday of the 1st week of year)

z~zzz:  (Specific GMT Timezone Abbreviation)
zzzz:   (Specific GMT Timezone Name)
Z:  +0000 (RFC 822 Timezone)