Question

I’m using NSArray *toWrite = [[items sortedArrayUsingFunction:comparator context:nil] copy]; within my code to sort the NSDictionaires in my NSArray.

Here is my C function for comparing:

static NSComparisonResult comparator( NSDictionary *d1, NSDictionary *d2, void *context )
{
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"EEE, dd/MM/yyyy"];
    NSDate *date1 = [dateFormatter dateFromString:[d1 objectForKey:@"date"]];
    NSDate *date2 = [dateFormatter dateFromString: [d2 objectForKey: @"dateString"]];
    NSLog(@"date1:%@",[dateFormatter stringFromDate:date1]);
    NSLog(@"date2:%@",[dateFormatter stringFromDate:date2]);
    [dateFormatter release];
    NSLog(@"COMPARE:%d",[date1  compare:date2]);
    return [date1  compare:date2];
}

And Here is the output when I run the App with 3 NSDictionaries in the NSArray:

date1:Thu, 17/11/2011
date2:(null)
COMPARE:0
date1:Sat, 19/11/2011
date2:(null)
COMPARE:0

By the way here is how one NSDictionary from my .plist file:

<dict>
    <key>date</key>
    <string>Thu, 17/11/2011</string>
    <key>duration</key>
    <string>120 min</string>
    <key>location</key>
    <string>BA708</string>
    <key>notes</key>
    <string>10 min reading time</string>
    <key>seat</key>
    <string>14</string>
    <key>time</key>
    <string>09:00</string>
    <key>unitName</key>
    <string>ROBOT SYSTEMS DESIGN</string>
</dict>

Answer 1

You’re using “date” for one key and “dateString” for the other:

NSDate *date1 = [dateFormatter dateFromString:[d1 objectForKey:@"date"]];
NSDate *date2 = [dateFormatter dateFromString: [d2 objectForKey: @"dateString"]];

According to the plist example you show, the key is “date.” Assuming you’re comparing apples to apples, that’s why date2 always comes up null.