NSMutableArray *siftArray = [NSMutableArrayarray];

    NSArray *sources =@[@"dfersa",@"adfae",@"frdg",@"rfde",@"drgs",@"wser",@"rfdt",@"pkoi"];

//    [self.sources addObjectsFromArray : [JKCountryResout searchCountryNameByStrings:@"china"]];

   for (NSString *strin self.sources){

       NSString *resoultStr = [str substringToIndex:1];

        [siftArrayaddObject:resoultStr];

    }

   NSSet *set = [NSSetsetWithArray:siftArray];

   NSArray *sortDesc = @[[[NSSortDescriptor alloc] initWithKey:nilascending:YES]];

   NSArray *sortSetArray = [set sortedArrayUsingDescriptors:sortDesc];

   NSLog(@"排序的结果 %@", sortSetArray);

tableview的索引值