Why headerView is always nil in numberOfRowsInSection? - ios

Question

I have to make a dynamic datasource for a table, that satisfies the criteria:
we do not know exact number of sections
we do not know exact title for header in section
we do not now how many rows it will be in each section each time
To detect number of rows per section I have the following code:
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let header = tableView.headerView(forSection: section)
return self.servicesData?.filter({ $0.clubName == header?.textLabel?.text }).count ?? 0
}
where servicesData is the object array that is to be filtered by the header title aka clubName. Titles are gathered from the object array.
For some reason I always get nil when try to access the header. So far I tried calling tableView(_:titleForHeaderInSection:) directly in numberOfRowsInSection but obviously with no luck.
Feedback much appreciated.

Answer 1

It is nil because it is not created at that moment. You should not use tableView.headerView(forSection: section) in numberOfRows. You should use the model from where you get the title to use it to filter in the array.
You should fetch all of your data before populating the table view and first. Then you should implement:
func numberOfSections(in tableView: UITableView) -> Int {
return headerModels.count
}
where headerModels it's an array of objects with your title and it's items like:
class HeaderModel {
let title: String
let items: [YourItem]
}
and then:
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return headerModels[section].items.count
}

Answer 2

So, as per #shurtugal 's solution it is possible to pass-in an array of objects to populate the table. I thought that creating a utility class for this very case may be too much. So here's the slightly altered way:
Consider a dictionary var servicesData = [String: [CustomObject]]() that is populated each time the ViewController shows up. The dictionary can have indefinite number of keys and indefinite number of values inside each key. Algorithm of populating the dictionary is taken from this answer.
Thereby, UITableViewDatasource methods can be defined like this:
func numberOfSections(in tableView: UITableView) -> Int {
self.servicesData.count
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return Array(self.servicesData.values)[section].count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
/* cell creation code code */
/// sample line
cell?.someLabel.text = Array(self.servicesData.values)[indexPath.section][indexPath.row]
return cell
}