How do I sort an array of custom objects on this property?

Question

I have an array containing custom objects with a property named seat. Seat can have values 1A, 1D , 1C , 1k , 2A, 2k, 2D, 2C.

Now these can be arranged in any order, and I want to sort them according to class, however the sorting only accounts for the seats numeric value and not A, C, D,or K.

I want the order to be 1A,1C,1D,1K and so on.

This is what I have implemented in the SeatDO object:

-(NSComparisonResult) compareBySeatNumber:(SeatDO*)other {
    NSComparisonResult result = NSOrderedSame;
    NSInteger seatNumber = [self.seat integerValue];
    NSInteger otherSeatNumber = [other.seat integerValue];

    if (seatNumber > otherSeatNumber) {
        result = NSOrderedDescending;
    } else if (seatNumber < otherSeatNumber) {
        result = NSOrderedAscending;
    }
    return result;
}

How do I make it consider the letters as well..?

Answer 1

Assuming that you convert the seat numbers to NSStrings

NSArray *sortedSeats = [seats sortedArrayUsingSelector:@selector(localizedStandardCompare:)]

should do the trick. Sorting strings will naturally follow the sort order you need.

Otherwise you could just use strings during the comparison with

[seats sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    return [[obj1 stringValue] localizedStandardCompare:[obj2 stringValue]];
}];

I assumed that stringValue is available for you custom object. If not, simply replace it with anything that will return a NSString description of your instances.

NOTE

As suggested by Alladinian, you want to use localizedStandardCompare: as opposed to caseInsensitiveCompare:, in order to the get the proper lexicographic order.

Answer 2

Use localizedStandardCompare: as the selector (Finder-like sorting)

[seats sortedArrayUsingSelector:@selector(localizedStandardCompare:)]

While caseInsensitiveCompare: might seem like correct, if you add a @"10D" or @"01C" seat it would appear in front of all others...