NSDate and NSDateFormatter issues

Question

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];

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"];

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]; 
}

The error I get is the following:

*** 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'

Solution

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.

For example:

[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
    }
}

Comments

[Roman]

I've ensured that's the case, although I think the formatting of cDate is what's breaking it. It is set to: 1972-01-01. That worked fine for when my format string was "yyyy-MM-dd". Now that it's "MMMM d, yyyy" it crashes.

[Ecton]

What is the value of "date" before assigning to the date picker? Is it outside of the minimum and maximum date values for the picker?

[Roman]

I believe the issue is NSDateFormatter doesn't know how to internet something in the format of say: 1990-01-01 and translate it to setDateFormat:@"MMMM d, yyyy", it is capable of doing it when the format string is "yyyy-MM-dd".

[Ecton]

The problem is that the date formatter's format is being set to MMMM d, yyyy, but you're giving it a date in a different format. My guess is that if you were to answer my question, you would notice that "date" was an invalid value. You'll need to parse the date with a matching format string.

[Ecton]

If your date is "1972-01-01", it will only be able to be parsed by a format of "yyyy-MM-dd". Thus, you must parse using that format. If you're wanting to accept two formats, you'll have to try once with one format, and then try to parse again using the other format.