iOS development tableView cell implementation code

#import ""

@interface ZCellGroupController ()<UITableViewDelegate, UITableViewDataSource>

@property (nonatomic, strong) UITableView *tableView;
@property (nonatomic, strong) NSArray *titleArray;//Group@property (nonatomic, strong) NSArray *friendsArray;//The corresponding content of each group@property (nonatomic, strong) NSMutableArray *selectedArr;//Storage the cell group that needs to be expanded
@end

@implementation ZCellGroupController


-(void)viewDidLoad {
  [super viewDidLoad];
   = [[NSMutableArray alloc]init];
  [self addTableView];
  [self addData];
}
- (void)addTableView{
  UITableView *tableView = [[UITableView alloc]initWithFrame:CGRectMake(0, 0, kSCREENWIDTH, kScreenHeight) style:UITableViewStyleGrouped];
   = tableView;
   = self;
   = self;
   = UITableViewCellSeparatorStyleSingleLine;
  [ addSubview:_tableView];
}
- (void)addData{
   = [NSArray arrayWithObjects:@"Friends",@"stranger", nil];
   = [NSArray arrayWithObjects:
                       @[@"A",@"B",@"C",@"D",@"E",@"F"],
                       @[@"Stranger 1",@"Stranger 2",@"Stranger 3",@"Stranger 4",@"Stranger 5",@"Stranger 6",@"Stranger 7",@"Stranger 8",@"Stranger 9",@"Stranger 10",@"Stranger 11",@"Stranger 12",@"Stranger 13",@"Stranger 14"],nil];
}

#pragma mark --tableViewDelegate

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
  return ;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
  NSString *sectionStr = [NSString stringWithFormat:@"%ld",(long)section];
  NSInteger num ;
  //If selectedArr does not contain section, the grouping returns number 0;  if ([ containsObject:sectionStr]) {
    NSArray *arrayData = [section];
    
    num =  ;
  }else{
    num = 0;
  }
  return num;
}
- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section{
  return 40;
}
- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section{
  UIView *view = [[UIView alloc]initWithFrame:CGRectMake(0, 0, kSCREENWIDTH, 40)];
   = [UIColor whiteColor];
  UILabel *titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, 5,kSCREENWIDTH-20 , 30)];
   = [section];
  [view addSubview:titleLabel];
  
  //Add a click event  UIButton *btn = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, kSCREENWIDTH, 40)];
   = 100+section;
  [btn addTarget:self action:@selector(viewBtnClick:) forControlEvents:UIControlEventTouchUpInside];
  [view addSubview:btn];
  return view;
}
- (void)viewBtnClick:(UIButton *)btn{
  NSString *string = [NSString stringWithFormat:@"%ld", - 100];
  if ([ containsObject:string]) {
    [ removeObject:string];
  }else{
    [ addObject:string];
  }
  NSLog(@"selectedArr:%@",);

  [_tableView reloadData];
}
- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section{
  return 10;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
  
  NSString *sectionStr = [NSString stringWithFormat:@"%ld",(long)];
  static NSString *cellID = @"testCellID";
  UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellID];
  if (!cell) {
    cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellID];
     = UITableViewCellSelectionStyleGray;

  }
  
  NSArray *arrayData = [];
  
  if ([ containsObject:sectionStr]) {
     = arrayData[];
  }
  return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{
  return 45;
}
@end