stringFromDate always NIL

问题

I know this is a repetitive question, but after searching for many similar questions on stackoverflow and google, none of the solutions worked for me.

I am tring to convert date which I receive from DB to string format to display in iPhone app.

I am converting date to string in following manner, but [dateFormat stringFromDate:beginDate] always return nil.

    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"MMM dd hh:mm a"];
    NSString *dateString = [dateFormat stringFromDate:beginDate];
    NSLog(@"date: %@", dateString);
    [dateFormat release];

The server NSDate received is of following format:

 2012-05-23 13:06:51.394+1000

and I want it to

 May 25 13:06 PM

Please help.

Thanks in advance.

回答1:

You need to convert your beginDate string to an actual NSDate first, and then do it:

NSString *beginDateString  = [arr_data objectAtIndex:1];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss.SSSZ"];
NSDate *beginDate = [formatter dateFromString:beginDateString];

[formatter setDateFormat:@"MMM dd hh:mm a"];
NSString *dateString = [formatter stringFromDate:beginDate];
NSLog(@"date: %@", dateString);

Note that you say in your question that you want it to output May 25 13:06 PM but it will actually output May 25 01:06 PM. (13:06 would be using 24 hour time instead of 12 hour time and wouldn't need the am/pm.)

回答2:

What is the type of beginDate? If it is NSString, then convert it to NSDate first, by using dateFromString method of NSDateFormatter.

EDIT2: (Fixed a typo and add full working example)

NSString *beginDate = @"2012-05-23 13:06:51.394+1000";
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

// Set the format of the dateFormatter to the date format of the server
dateFormatter.dateFormat = @"yyyy-MM-dd HH:MM:ss.SSSZ";
// Convert the NSString to NSDate
NSDate* date = [dateFormatter dateFromString: beginDate];

// Set the format of dateFormatter to your own format
dateFormatter.dateFormat = @"MMM dd hh:mm a";
// Convert NSDate to your own format of date
beginDate = [dateFormatter stringFromDate: date];

回答3:

There is nothing wrong in above code, it works fine with current date. Just replace

NSString *dateString = [dateFormat stringFromDate:beginDate];

NSString *dateString = [dateFormat stringFromDate:[NSDate date]];

and will work.

It seems that there is problem with your beginDate.

回答4:

May be your beginDate's format is like "2013-09-29 14:57:48.0",but the dataFormate is

[dFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"]

change to "yyyy-MM-dd HH:mm:ss.0" will be OK

回答5:

You need to call setDateFormat before calling stringFromDate

 NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"HH:mm dd/MM/yyyy"];
 NSString * dateString =[dateFormatter stringFromDate:someDate];

来源：https://stackoverflow.com/questions/10713024/stringfromdate-always-nil

标签

iphone

objective-c

ios

ipad

nsdate