TableView skipping when exapnded section cells - ios

Question

I try to implement the collapse/expand system for table view sections. When the user tapped on the section header, then it will inserts cells into section when tapped one more time on the same section header then it will deleting cells from section making "collapse" effect.
The problem is when I try to expand more than 2 sections starting from the bottom. Tapping section which has at least one cell shift whole content without animation to lower section position.
I use auto-layout from code and RxDataSource.
Here is how I bind data source:
let dataSourceForPurchasersList = RxTableViewSectionedAnimatedDataSource<AnimatableSectionModel<ExpandableSectionModel, CustomerCellModel>>(configureCell: { (dataSource, tableView, indexPath, cellModel) -> UITableViewCell in
let cell = tableView.dequeueReusableCell(withIdentifier: GuestTableViewCell.reuseIdentifier, for: indexPath) as? GuestTableViewCell
cell?.setupCell(model: cellModel)
return cell ?? UITableViewCell()
})
viewModel.dataSourceBehaviorPurchasersList
.bind(to: self.ordersTableView.rx.items(dataSource: dataSourceForPurchasersList))
.disposed(by: self.disposeBag)
Here is how I handle section expand:
func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
guard let viewModel = self.viewModel else { return nil }
let header = tableView.dequeueReusableHeaderFooterView(withIdentifier: CustomersSectionHeader.reuseIdentifier) as? CustomersSectionHeader
...
guard let models = try? modelsBehavior.value() else { return nil }
let dataSourceSectionModel = models[section]
header?.configView(model: dataSourceSectionModel)
header?.tapClosure = { [weak modelsBehavior, weak header] in
dataSourceSectionModel.expanded = !dataSourceSectionModel.expanded
header?.updateSelectorImageView()
modelsBehavior?.onNext(models)
}
return header
}
Presenting the problem
#edit
Solution:
I observed that the shift of content is equal to the section header height by implementing scrollViewDidScroll(_ scrollView: UIScrollView) function and it depends on the table view internal logic. I set headerHeight and estimatedHeight of the section header to equal value then I used this code:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let divValue: CGFloat
if self.guestsTableView.delegate === scrollView.delegate {
divValue = self.guestsTableView.estimatedSectionHeaderHeight
} else {
divValue = self.ordersTableView.estimatedSectionHeaderHeight
}
let diff = abs(self.scrollViewOffsetLastY - scrollView.contentOffset.y)
let rest = diff.truncatingRemainder(dividingBy: divValue)
if rest == 0 {
scrollView.contentOffset.y = self.scrollViewOffsetLastY
}
self.scrollViewOffsetLastY = scrollView.contentOffset.y
}