NSDate和NSDateFormatter问题 [英] NSDate and NSDateFormatter issues

问题描述

我有点难以理解为什么下面的代码崩溃了我的一个应用程序：

I'm having slight difficulty in understanding why the following code is crashing an app of mine:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"MMMM d, yyyy"];
NSDate *date = [dateFormatter dateFromString:cDate];
datePicker.date = date;
NSString *dateStr = [dateFormatter stringFromDate:date]; 
[dateLabel setText:dateStr];
[dateFormatter release];

如果我评论上面的内容，此外，如果我将日期格式更改为以下，则不会发生崩溃：

If I comment the above out, app is fine. Also if I change the date format to the following no crash happens:

[dateFormatter setDateFormat:@"yyyy-MM-dd"];

在我的 UIDatePicker 委托中，代码看起来像下面的（和工程很好）：

In my UIDatePicker delegate, I have repeated code that looks like the following (and works great):

-(IBAction)datePickerValueChanged:(id)sender 
{
    NSDate *date = [datePicker date];       
    NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
    [dateFormatter setDateFormat:@"MMMM d, yyyy"];
    NSString *dateStr = [dateFormatter stringFromDate:date]; 
    [dateLabel setText:dateStr]; 
}

我得到的错误如下：

*** Assertion failure in -[UIDatePickerView _updateBitsForDate:andReload:animateIfNeeded:], /SourceCache/UIKit/UIKit-747.38/UIDatePicker.m:892

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid parameter not satisfying: date'

推荐答案

问题是输入日期是以yyyy-MM-dd格式，但是你使用dateFromString的日期格式化格式化为MMMM d，yyyy。

The problem is that the input date is in the "yyyy-MM-dd" format, but the date formatter you're using with dateFromString is formatted "MMMM d, yyyy". You'll need to try parsing with both formats if you're desiring both formats to be accepted.

例如：

[dateFormatter setDateFormat:@"MMMM d, yyyy"];
NSDate *date = [dateFormatter dateFromString:cDate];
if (date == nil) {
    [dateFormatter setDateFormat:@"yyyy-MM-dd"];
    date = [dateFormatter dateFromString:cDate];
    if (date == nil) {
        // Handle the situation where the date string could not be parsed
    }
}

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