iPhone, if I'm converting a date string from one format to another, to store it, do I have to convert it to a date, how?

I need to show a date in a certain format 开发者_JAVA技巧on screen, but I need to store the date as a string in another format. I think this means I have to convert it to a date and back to a string.

How do i do this ?

I have already figured out how to convert my string to a date, however build analyser gives me a warning.

I want to convert the string from dd MM yyyy to yyyy-MM-dd

He my code so far...

NSString *startDateString = btnStartDate.titleLabel.text;
NSDateFormatter *dateStartFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateStartFormatter setDateFormat:@"dd MM yyyy"];
NSDate *datStartDate = [[NSDate alloc] init];
datStartDate = [dateStartFormatter dateFromString:startDateString];

The analyzer warns you of a leak. First, you assign a new object to datStartDate, and then you store a new value with datStartDate = [dateStartFormatter dateFromString:startDateString]; without releasing the previous object first.

So instead of:

NSDate *datStartDate = [[NSDate alloc] init];
datStartDate = [dateStartFormatter dateFromString:startDateString];

You should just write:

NSDate *datStartDate = [dateStartFormatter dateFromString:startDateString];

Well you're allocating space for datStartDate for a new NSDate, then replacing it with a completely new NSDate from your date formater (now you have memory set aside for the first NSDate that is never going to be used)

Use this:

NSDate* datStartDate = [dateStartFormater dateFromString:startDateString];

then use your dateStartFormater or another NSDateFormatter to turn your date into the required string like so:

 [dateStartFormatter setDateFormat:@"yyyy MM dd"];
 NSString* formatedDate = [dateStartFormater stringFromDate:datStartDate];