xcode 使用 NSDateFormatter 设置 UIDatePicker 日期
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Setting UIDatePicker date with NSDateFormatter
提问by schaz
I am trying to initialize a UIDatePicker with a date that was returned to me from that date picker earlier in my session. This is part of an inventory program that needs to get the date that in inventory item was last calibrated.
我正在尝试使用一个日期来初始化 UIDatePicker，该日期是在我的会话早些时候从该日期选择器返回给我的。这是库存程序的一部分，需要获取库存项目上次校准的日期。
Using this code I receive a date/time string:
使用此代码我收到一个日期/时间字符串：
NSDate *choice = [pickedDate date];
calDate = [[NSString alloc] initWithFormat:@"%@", choice];
I end up with the following string in calDate: 2011-11-11 21:56:38 +0000
我在 calDate 中得到以下字符串：2011-11-11 21:56:38 +0000
I am trying to set my date picker with the following code:
我正在尝试使用以下代码设置我的日期选择器：
NSDate *date = [[[NSDate alloc] init] retain];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSLog(@"cal date = %.@.",drawingInfo.drawingDate);
if([calDate length] != 0) {
date = [dateFormatter dateFromString:calDate];
if(date != nil) {
[pickedDate setDate:date animated:NO];
}
}
The NSLog verifies that the string is still in tact. If I put a breakpoint on the if(date != nil) it shows me that date = nil.
NSLog 验证字符串是否仍然完整。如果我在 if(date != nil) 上放置一个断点，它会显示 date = nil。
Thanks in advance.
提前致谢。
回答by bryanmac
You're missing the Z format specifier in the date format.
您在日期格式中缺少 Z 格式说明符。
This code:
这段代码：
NSString *calDate = @"2011-11-11 21:56:38 +0000";
NSDate *date = [[[NSDate alloc] init] retain];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss Z"];
// right here ^
date = [dateFormatter dateFromString:calDate];
NSLog(@"date:%@", date);
Outputs:
输出：
2012-01-03 20:14:15.258 Craplet[38753:707] date:2011-11-11 21:56:38 +0000
Without the Z:
没有 Z：
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
It outputs:
它输出：
2012-01-03 20:16:10.456 Craplet[38885:707] date:(null)
If the format cannot be matched to the date string, it returns nil
如果格式不能与日期字符串匹配，则返回 nil
