尝试使用块

[arr sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {

    if ([obj1 intValue] == [obj2 intValue])
        return NSOrderedSame;

    else if ([obj1 intValue] < [obj2 intValue])
        return NSOrderedAscending;

    else
        return NSOrderedDescending;

}];