Open Radar

 
Area:
UIKit

Summary:
When the UITableViewDelegate optional methods are implemented, in a certain configuration the section header for the 0th section will not be populated and the delegate method is not called

Reproduced always

Steps to Reproduce:
I've removed computation logic for clarity and only left the final flow configuration leading to the bug.

Notice that when - tableView estimatedHeightForHeaderInSection:section
returns "0", the 0th section won't have a title. 

If you return "10" , the 0th section will have a header



#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  UITableView *tv = [[UITableView alloc] initWithFrame:self.view.bounds style:UITableViewStyleGrouped];
  tv.dataSource = (id <UITableViewDataSource>)self;
  tv.delegate = (id <UITableViewDelegate>)self;
  [tv registerClass:[UITableViewCell class] forCellReuseIdentifier:@"cell"];
  [self.view addSubview:tv];
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    CGFloat f = [tv sectionHeaderHeight];
    NSLog(@"%@",@(f).description);
  });
}



- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
  return 10;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
  return 10;
}
// Row display. Implementers should *always* try to reuse cells by setting each cell's reuseIdentifier and querying for available reusable cells with dequeueReusableCellWithIdentifier:
// Cell gets various attributes set automatically based on table (separators) and data source (accessory views, editing controls)
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
  return [tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
}

- (nullable NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
  return @(section).description;
}

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section
{
  return -1;
}

//*******

- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section
{
  return -1;
}

// Use the estimatedHeight methods to quickly calcuate guessed values which will allow for fast load times of the table.
// If these methods are implemented, the above -tableView:heightForXXX calls will be deferred until views are ready to be displayed, so more expensive logic can be placed there.
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
  return UITableViewAutomaticDimension;
}

////*******
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForHeaderInSection:(NSInteger)section
{
  return 0;
}
//- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForFooterInSection:(NSInteger)section
//{
//  return 0;
//}

// Section header & footer information. Views are preferred over title should you decide to provide both

- (nullable UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section   // custom view for header. will be adjusted to default or specified header height
{
  return nil;
}
- (nullable UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section   // custom view for footer. will be adjusted to default or specified footer height

{
  return nil;
}
@end


Expected Results:
0th section should have a header title

Actual Results:
0th section doesn't have a title