Sorting NSArray with blocks

iOS4 blocks introduced a new way to sort NSArray. There is no need to provide selectors or functions as comparators any more. All you need is to provide a comparator block which returns one of 3 NSComparator values and take to objects as an argument. The input and output is same as for the outdated selector/function way (you can hardly change general comparator interface) but now your comparator block captures you function context! Additionally all the code is in the same place.

Below is a bit of my recent work code that changes the order of sorting based on the class instance variable m_seatQuality value:

featuresArray = [[unsortedFeaturesArray sortedArrayUsingComparator: ^(id a, id b) {

DMSeatFeature *first = ( DMSeatFeature* ) a;

DMSeatFeature *second = ( DMSeatFeature* ) b;

if ( first.quality == second.quality )

return NSOrderedSame;

else

{

if ( eSeatQualityGreen == m_seatQuality

|| eSeatQualityYellowGreen == m_seatQuality

|| eSeatQualityDefault == m_seatQuality )

{

if ( first.quality < second.quality )

return NSOrderedAscending;

else

return NSOrderedDescending;

}

else // eSeatQualityRed || eSeatQualityYellow

{

if ( first.quality > second.quality )

return NSOrderedAscending;

else

return NSOrderedDescending;

}

}

}] retain];