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    <p>I would create a new class called <code>ItemGroup</code>, and then add an extra ivar called <code>group</code> to your item class:</p> <pre><code>@interface ItemGroup : NSObject { NSNumber * time; } @property (nonatomic, copy) time; @end @interface ItemClass : NSobject { NSString * name; NSNumber * time; ItemGroup * group; } @property (nonatomic, copy) NSString * name; @property (nonatomic, copy) NSNumber * time; @property (nonatomic, assign) ItemClass * group; // note: must be assign @end </code></pre> <p>Then, you could do the following:</p> <pre><code>NSMutableDictionary * groups = [NSMutableDictionary dictionaryWithCapacity:0]; for (ItemClass * item in sourceData) { ItemGroup * group = [groups objectForKey:item.name]; if (group == nil) { group = [[ItemGroup alloc] init]; [groups setObject:group forKey:item.name]; [group release]; group.time = item.time; } else if (item.time &lt; group.time) { group.time = item.time; } item.group = group; } </code></pre> <p>This code loops through the unsorted array, keeping track of the minimum time for each group, and also <em>setting</em> the group for each item. With that complete, you simply sort on <code>group.time</code> and <code>time</code>:</p> <pre><code>NSSortDescriptor * groupSorter; groupSort = [NSSortDescriptor sortDescriptorWithKey:@"group.time" ascending:YES]; NSSortDescriptor * timeSorter; timeSort = [NSSortDescriptor sortDescriptorWithKey:@"time" ascending:YES]; NSArray * sortDescriptors = [NSArray arrayWithObjects:groupSort, timeSort, nil]; NSArray * sorted = [sourceData sortedArrayUsingDescriptors:sortDescriptors]; </code></pre> <p>And that should do the trick!</p> <p><strong><em>UPDATE</em></strong>: Note that you could get <em>much</em> better performance if you were able to assign the groups straight out of the gate. Something like this:</p> <pre><code>@interface ItemGroup : NSObject { NSString * name; NSNumber * time; } @property (nonatomic, copy) NSString * name; @property (nonatomic, copy) NSSNumber * time; @end @interface ItemClass : NSObject { ItemGroup * group; NSNumber * time; } @property (nonatomic, retain) ItemGroup * group; @property (nonatomic, copy) NSNumber * time; @end </code></pre> <p>Now, if you maintain a list of groups somewhere (they could even go in an array somewhere, if need be):</p> <pre><code>ItemGroup * group_A = [[ItemGroup alloc] init]; group_A.name = @"A"; ItemGroup * group_B = [[ItemGroup alloc] init]; group_B.name = @"B"; ... </code></pre> <p>And instead of setting the <em>names</em> of your data items, you set their group:</p> <pre><code>someItem.group = group_A; someItem.time = GetSomeRandomTimeValue(); [sourceData addObject:someItem]; .... </code></pre> <p>This would greatly simplify the loop used to set group times:</p> <pre><code>for (ItemClass * item in sourceData) { if (item.time &lt; group.time) { group.time = item.time; } } </code></pre> <p>And, if you really wanted to be <em>blazing</em> fast about it, you could even modify the property setter for your <code>time</code> property to set the group times on the fly:</p> <pre><code>@implementation ItemClass - (void)setTime:(NSNumber *)newTime { if (newTime &lt; group.time) { group.time = newTime; } time = [newTime copy]; } @end </code></pre> <p>Note that you would have to be sure that <code>group</code> had been set before you set the time. With this in place, you wouldn't need that sorting loop at all. The sortDescriptors would be enough.</p>
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    1. POHelp sorting an NSArray across two properties (with NSSortDescriptor?)
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    1. COI understand this, but I don't think this answers the question. I am not sorting by name, I need to rank and group the names based on what's the smallest time value for a given name.
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    2. COAh. Now I see. That's much more interesting.
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    3. CODo you define the type of object that gets stored in the original array? i.e. is it a custom class that you can add ivars to?
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