ECGraph not working on device, but works on simula

问题:

is there any reason why ECGraph would run fine on the simulator, but yet give me this error when i run it on my device:

 2012-08-24 01:57:18.543 Portfolio[3538:907] *** -[__NSCFCalendar                 components:fromDate:toDate:options:]: fromDate cannot be nil
 I mean really, what do you think that operation is supposed to mean with a nil fromDate?
 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                      0x37a1d78f <redacted> + 86
1   Portfolio                           0x000a0d1f -[ECGraph(Private) getDaysFrom:To:] + 202
2   Portfolio                           0x000a1577 -[ECGraph(Private) getXDaysFromLines:minDate:] + 502
3   Portfolio                           0x000a2623 -[ECGraph drawCurveWithLines:lineWidth:color:] + 978
4   Portfolio                           0x000a716f -[GraphView drawRect:] + 2682
5   UIKit                               0x38b1811d <redacted> + 364
6   QuartzCore                          0x39468035 <redacted> + 112
7   QuartzCore                          0x39467771 <redacted> + 1808
8   QuartzCore                          0x39466f45 <redacted> + 980
9   QuartzCore                          0x39466a7b <redacted> + 202
10  QuartzCore                          0x3953a9f5 <redacted> + 24
11  QuartzCore                          0x394663d3 <redacted> + 238
12  QuartzCore                          0x39466119 <redacted> + 316
13  QuartzCore                          0x3945dfe1 <redacted> + 60
14  CoreFoundation                      0x37a4f18d <redacted> + 20
15  CoreFoundation                      0x37a4d3f9 <redacted> + 276
16  CoreFoundation                      0x37a4d74f <redacted> + 742
17  CoreFoundation                      0x379cbc1d CFRunLoopRunSpecific + 356
18  CoreFoundation                      0x379cbaa9 CFRunLoopRunInMode + 104
19  GraphicsServices                    0x3a88f33b GSEventRunModal + 74
20  UIKit                               0x38b35535 UIApplicationMain + 1120
21  Portfolio                           0x00094e7d main + 152
22  Portfolio                           0x00094de0 start + 40

)

回答1:

You are trying to get NSDateComponents from a nil NSDate like that:

NSCalendar* gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate* fromDate = nil;
NSDate* toDate = [NSDate date];
unsigned int components = NSYearCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit | NSWeekCalendarUnit | NSWeekdayCalendarUnit | NSHourCalendarUnit;
NSDateComponents* dateComponents = [gregorian components:uintFlags fromDate:fromDate  toDate:toDate  options:0];

Probably a simple check can be useful:

NSDate* fromDate = nil;
NSDate* toDate = [NSDate date];

NSDateComponents* dateComponents = nil;

if(fromDate != nil)
{
 NSCalendar* gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
 unsigned int components = NSYearCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit | NSWeekCalendarUnit | NSWeekdayCalendarUnit | NSHourCalendarUnit;
 dateComponents = [gregorian components:uintFlags fromDate:fromDate  toDate:toDate  options:0];
}

回答2:

Your device is using a different Region Format than your simulator.

If you match those (in Settings -> General -> International), then they should show the same result. In my case, when doing this, they both failed, but the simulator didn't give the same log as the device so I nearly missed it.

I assume you are using an NSDateFormatter to format some string-date to NSDate as I was. In that case you have to make sure that this won't depend on what kind of region the phone is, and set the solution to always be the same, whereever you are.

[df setLocale:([[NSLocale alloc] initWithLocaleIdentifier:@"en_UK"])];
// df being the NSDateFormatter-object

This tells the formatter to format using UK standards, which was needed in my case. Enter your needed country code, i.e en_US etc.

Sti