How to add letter index for iOS tabview

//The system gets the first letter- (NSString *) pinyinFirstLetter:(NSString*)sourceString {
 NSMutableString *source = [sourceString mutableCopy];
 CFStringTransform((__bridge CFMutableStringRef)source, NULL, kCFStringTransformMandarinLatin, NO);
 CFStringTransform((__bridge CFMutableStringRef)source, NULL, kCFStringTransformStripDiacritics, NO);//This line is de-toned return source;
}

#import ""
#import ""
#import ""

@interface ViewController (){
 NSMutableArray<Person *> *dataArray;
}
//Array of pinyin initial letters after sorting@property(nonatomic,strong)NSMutableArray *indexArray;
//Sorted result array@property(nonatomic,strong)NSMutableArray *letterResultArr;
@end

@implementation ViewController

- (void)viewDidLoad {
 [super viewDidLoad];

 //Simulate data loading to get Person's array in dataArray [self loadData];

 //BMChineseSort file contains two array sorting functions for cell data and letters to the right //Sort Person array by Chinese according to the name attribute of the Person object //The data of each cell is sorted  = [BMChineseSort IndexWithArray:dataArray Key:@"name"];
 //The alphabet array on the left has been sorted  = [BMChineseSort sortObjectArray:dataArray Key:@"name"];

 UITableView *table = [[UITableView alloc] initWithFrame:];
  = self;
  = self;
 [ addSubview:table];
}
//Load simulated data-(void)loadData{
 NSArray *stringsToSort=[NSArray arrayWithObjects:
       @"Li Bai",@"Zhang San",
       @"Chongqing",@"weight",
       @"adjust",@"Call",
       @"noob",@"Xiao Ming",@"Qianjue",
       @"Wang Jiaju", @"mouse",@"hello",@"How beautiful",@"KFC",@"##",
       nil];

 //Simulate the array object received by the network request Person array dataArray = [[NSMutableArray alloc] initWithCapacity:0];
 for (int i = 0; i<[stringsToSort count]; i++) {
  Person *p = [[Person alloc] init];
   = [stringsToSort objectAtIndex:i];
   = i;
  [dataArray addObject:p];
 }
}

#pragma mark - UITableView -
//section's titleHeader- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
 return [ objectAtIndex:section];
}
//section row count-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
 return [ count];
}
//The number of sections per group- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
 return [[ objectAtIndex:section] count];
}
//The index array on the right side of section-(NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView{
 return ;
}
//Call the corresponding relationship between the index and section when clicking on the index entry on the right- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index{
 return index;
}
//Return to cell- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
 UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CELL"];
 if (cell == nil){
  cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"CELL"];
 }
 //Get the corresponding Person object <Replace with your own model object> Person *p = [[ objectAtIndex:] objectAtIndex:];
  = ;
 return cell;
}
@end