我正在分析日期，并希望将其转换为用户当前所在的时区。此外，我想显示一个倒计时，显示剩余的天数，直到特定日期。这是我的代码：
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *MyIdentifier = @"MyIdentifier";
MyIdentifier = @"tblCellView";
TableCellView *cell = (TableCellView *)[tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if(cell == nil) {
[[NSBundle mainBundle] loadNibNamed:@"TableCellView" owner:self options:nil];
cell = tblCell;
}
NSString *cellstring = [NSString stringWithFormat:@"%@", [[self.parseResults objectAtIndex:indexPath.row] objectForKey:@"title"]];
NSString *cellnumber = [NSString stringWithFormat:@"%@", [[self.parseResults objectAtIndex:indexPath.row] objectForKey:@"number"]];
NSString *epinumber = [cellnumber stringByReplacingOccurrencesOfString:@"-" withString:@""];
NSString *celldescription = [NSString stringWithFormat:@"%@",[[self.parseResults objectAtIndex:indexPath.row] objectForKey:@"date"]];
//NSLog(@"%@", celldescription);
//celldescription returns a value
NSString *finalString = [celldescription stringByReplacingOccurrencesOfString:@"EST" withString:@""];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease]];
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithName:@"EST"]];
// this is imporant - we set our input date format to match our input string
// if format doesn't match you'll get nil from your string, so be careful
[dateFormatter setDateFormat:@"EEE, dd MMM yyyy HH:mm:ss"];
NSDate *dateFromString = [[NSDate alloc] init];
// voila!
dateFromString = [dateFormatter dateFromString:finalString];
NSDateFormatter *dateFormatter1 = [[NSDateFormatter alloc] init];
[dateFormatter1 setDateFormat:@"EEE, dd MMM yyyy HH:mm aaa"];
NSString *dateDisplay = [dateFormatter1 stringFromDate:dateFromString];
[dateFormatter release];
NSCalendar *calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]autorelease];
int units = NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
NSDateComponents *components = [calendar components:units fromDate:[NSDate date] toDate:dateFromString options:0];
NSString *string = [NSString stringWithFormat:@"%d", [components day]];
if (indexPath.row == 0) {
cell.cellText.textColor = [UIColor redColor];
} else {
cell.cellText.textColor = [UIColor blackColor];
}
[cell setLabelText:cellstring];
[cell setDateText:dateDisplay];
[cell setCountText:string];
[cell setNumberText:epinumber];
return cell;
}
但我总是收到以下错误：
2012-12-29 13:10:23.139 spncountdown[87678:c07] *** -[__NSCFCalendar components:fromDate:toDate:options:]: toDate cannot be nil
I mean really, what do you think that operation is supposed to mean with a nil toDate?
An exception has been avoided for now.
A few of these errors are going to be reported with this complaint, then further violations will simply silently do whatever random thing results from the nil.
Here is the backtrace where this occurred this time (some frames may be missing due to compiler optimizations):
(
0 CoreFoundation 0x012c1c78 -[__NSCFCalendar components:fromDate:toDate:options:] + 200
1 spncountdown 0x000340bf -[SixthViewController convertWork] + 831
2 spncountdown 0x00033c14 -[SixthViewController tableView:cellForRowAtIndexPath:] + 820
3 UIKit 0x020988fb -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 412
4 UIKit 0x020989cf -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:] + 69
5 UIKit 0x020811bb -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1863
6 UIKit 0x02091b4b -[UITableView layoutSubviews] + 241
7 UIKit 0x0202e2dd -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 279
8 libobjc.A.dylib 0x030ad6b0 -[NSObject performSelector:withObject:] + 70
9 QuartzCore 0x01dcdfc0 -[CALayer layoutSublayers] + 240
10 QuartzCore 0x01dc233c _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 468
11 QuartzCore 0x01dc2150 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
12 QuartzCore 0x01d400bc _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 324
13 QuartzCore 0x01d41227 _ZN2CA11Transaction6commitEv + 395
14 QuartzCore 0x01de3b50 +[CATransaction flush] + 52
15 UIKit 0x01ff3edf _afterCACommitHandler + 132
16 CoreFoundation 0x0127aafe __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 30
17 CoreFoundation 0x0127aa3d __CFRunLoopDoObservers + 381
18 CoreFoundation 0x012587c2 __CFRunLoopRun + 1106
19 CoreFoundation 0x01257f44 CFRunLoopRunSpecific + 276
20 CoreFoundation 0x01257e1b CFRunLoopRunInMode + 123
21 GraphicsServices 0x03b127e3 GSEventRunModal + 88
22 GraphicsServices 0x03b12668 GSEventRun + 104
23 UIKit 0x01fddffc UIApplicationMain + 1211
24 spncountdown 0x00003222 main + 130
25 spncountdown 0x00003155 start + 53
)
答案 0 :(得分：2)
很明显，您的dateFromString是nil，这可能是因为日期格式问题。尝试打印格式化字符串并理解NSDateFormatter未正确解析它的原因。
答案 1 :(得分：0)
当您NSLog打印时：Wed, 27 Feb 2013 21:00:00
使用此代码：
NSString *finalString=@"Wed, 27 Feb 2013 21:00:00";
NSDateFormatter *dateFormatter2=[NSDateFormatter new];
[dateFormatter2 setDateFormat:@"EEE, dd MMM yyyy HH:mm:ss"];
NSLog(@"finalString: %@",[dateFormatter2 dateFromString:finalString]);
NSDate *dateFromString =[dateFormatter2 dateFromString:finalString];
[dateFormatter2 setDateFormat:@"dd MMM YYYY"];
NSLog(@"dateFromString : %@",[dateFormatter2 stringFromDate:dateFromString]);
输出：
finalString: 2013-02-27 15:30:00 +0000
dateFromString : 27 Feb 2013
答案 2 :(得分：0)
我为我解决了这个问题。我希望这对任何人都有帮助。我的问题是评论的代码。我用新编写的代码解决了这个问题，这些代码低于这个注释代码。代码如下：
// NSDateFormatter *df = [[NSDateFormatter alloc] init];
// df.dateStyle = NSDateFormatterMediumStyle;
//
// NSCalendar *calendar = [NSCalendar currentCalendar];
// int year = [[calendar components:NSYearCalendarUnit fromDate:[datePickerView date]] year];
// int month = [[calendar components:NSMonthCalendarUnit fromDate:[datePickerView date]] month];
// int day = [[calendar components:NSDayCalendarUnit fromDate:[datePickerView date]] day];
//
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit fromDate:[datePickerView date]];
NSInteger day = [components day];
NSInteger month = [components month];
NSInteger year = [components year];
date = [NSString stringWithFormat:@"%d-%d-%d",year,month, day];
NSLog(@"Updated Date: %@",date);
答案 3 :(得分：0)
我解决了我的问题。我在下面的样本中传递'nil'作为'date'。
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *comps = [gregorian components:NSWeekdayCalendarUnit fromDate:date];