How to sort NSArray with date time values? - iphone

Question

I have an NSArray containing date/time NSStrings in the following format:
2/2/2011 2:46:39 PM
2/4/2011 11:59:47 AM
…
where the date is represented as month/day/year.
How do I sort this NSArray making sure the newest date/times are at the top?

Answer 1

When you’re dealing with dates, use NSDate instead of NSString. Also, it’s important to consider the time zone — does the Web service provide dates in UTC or some other time zone?
You should first convert your array of strings into an array of dates. Otherwise, you’d be converting a string to a date whenever it is used for comparison, and there will be more comparisons than the number of strings.
For example:
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
[formatter setDateFormat:#"MM/DD/YYYY hh:mm:ss a"];
NSMutableArray *dateArray = [NSMutableArray array];
for (NSString *dateString in array) {
NSDate *date = [formatter dateFromString:dateString];
if (date) [dateArray addObject:date];
// If the date is nil, the string wasn't a valid date.
// You could add some error reporting in that case.
}
This converts array, an array of NSStrings, to dateArray, a mutable array of NSDates. The date formatter uses the system time zone. If you want to use UTC as the time zone:
NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
[formatter setDateFormat:#"MM/DD/YYYY hh:mm:ss a"];
[formatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
Having done that, sorting the array is trivial:
[dateArray sortUsingSelector:#selector(compare:)];

Answer 2

Use method compare to compare two dates,
Sample NSDate comparision,
NSDate *dateOne = [NSDate dateWithString:#"2008-12-04 03:00:00 +0900"];
NSDate *dateTwo = [NSDate dateWithString:#"2008-12-04 04:00:00 +0900"];
switch ([dateOne compare:dateTwo]){
case NSOrderedAscending:
NSLog(#”NSOrderedAscending”);
break;
case NSOrderedSame:
NSLog(#”NSOrderedSame”);
break;
case NSOrderedDescending:
NSLog(#”NSOrderedDescending”);
break;
}
Use you own logic to sort

Answer 3

use this
NSMutableArray *mutArr=[yourArray mutableCopy];//convert your NSArray into mutable array
NSDateFormatter *df=[[[NSDateFormatter alloc] init] autorealese];
[df setDateFormat:#"MM/DD/YYYY hh:mm:ss a"];
NSDate *compareDate;
NSInteger index;
for(int i=0;i<[mutArray count];i++)
{
index=i;
compareDate=[df dateFromString:[mutArray objectAtIndex:i]];
NSDate *compareDateSecond;
for(int j=i+1;j<counter;j++)
{
compareDateSecond=[df dateFromString:[mutArr objectAtIndex:j]];
NSComparisonResult result = [compareDate compare:compareDateSecond];
if(result == NSOrderedAscending)
{
compareDate=compareDateSecond;
index=j;
}
}
if(i!=index)
[mutArr exchangeObjectAtIndex:i withObjectAtIndex:index];
}
}
NSLog(#"%#",mutArr);