Capturing multiple values from UITableView with Swift - swift

Question

I'm trying to use a uitableview as a picker to allow the user to make multiple selections. I've set the tableview up to allow this and my coreData has a one-to-many relationship to allow for multiple values. My problem is that I cannot figure out how to capture the selected rows as values in my coreData.
I populate the table by fetching data from my 'Players' entity and storing it in this variable:
var playerPickerData = [NSManagedObject]()
I am guessing that I need to do something with the selectedrowsatindexpaths function to then extract the values back out of playerPickerData to be able to then add them to my 'Match' entity (which is linked to my players entity with a one-to-many relationship).
The code I have to populate my table cells is:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = playersPicker.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
cell.accessoryType = cell.isSelected ? .checkmark : .none
cell.selectionStyle = .none
let fName = playerPickerData[indexPath.row].value(forKey: "firstName") as! String
let lName = playerPickerData[indexPath.row].value(forKey: "lastName") as! String
let playersNameData = "\(fName) \(lName)"
cell.textLabel?.text = playersNameData
return cell
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
tableView.cellForRow(at: indexPath)?.accessoryType = .checkmark
selectedIndexPaths.append(indexPath as NSIndexPath)
}
func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
tableView.cellForRow(at: indexPath)?.accessoryType = .none
}
I have a UIPickerView that is used to select one value ('Game Name') and I can capture what I need to from this without issue by using the following on my SavePressed function:
let newMatch = NSEntityDescription.insertNewObject(forEntityName: "Match", into: context)
let selectedGame = pickerData[gamePicker.selectedRow(inComponent: 0)]
newMatch.setValue(selectedGame, forKey: "game")
I just need to know how i can save multiple values forKey = "players". Any advice on how/where to do this in my code would be very much appreciated.
If I can provide any more information then please let me know.
I genuinely cannot find anything that answers these questions here or elsewhere online. I think this might relate but I cannot translate it to my needs: Saving multiple values from a UITableView

Answer 1

I just need to know how i can save multiple values forKey = "players".
Always read the documentation of methods you are using when questions arise. The documentation of NSManagedObject.setValue(:forKey:) states:
If key identifies a to-one relationship, relates the object specified by value to the receiver, unrelating the previously related object if there was one. Given a collection object and a key that identifies a to-many relationship, relates the objects contained in the collection to the receiver, unrelating previously related objects if there were any.
So as long as you can construct and maintain a Set (Core Data uses sets to store to-many relationships) of your selected NSManagedObjects, you can simply do something along the lines of:
selectedObjects = [NSManagedObject]() // Fill this Array
parent.setValue(Set(selectedObjects), forKey: "key")
and it will automatically reset the to-many relationship, adding any new items and subtracting any that are not contained in the new collection.
It looks like you are maintaining a selectedIndexPaths array. In that case, you could do:
selectedIndexPaths.map { playerPickerData[$0.row] }
to get the selected objects, assuming your table view has a single section. You'll then need to turn that into a Set as displayed above. You could also collect the selected index paths as a set in the first place, but then after you map it it will be an Array again anyway.
PS
Note that in your didSelectRow you add the selected index paths to selectedIndexPaths, but you never remove them from selectedIndexPaths in didDeselectRow.