Single table view through two different NSFetchedResultsControllers with sections - ios

Question

Good morning to everyone. I am using Swift 3.1.1, Xcode 8.3.2. I need to connect a single Table View to two different tables (entities) in Core Data through two different NSFetchedResultsControllers. I have created two NSFetchedResultsControllers, and even fetched data from table but I faced problem how to tell Table View that first controller should response for section one and second controller should be responsible for section two.
I can show you the code:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var tv: UITableView!
#IBAction func pressed(_ sender: UIButton) {
ModelA.read { table1 in
ModelB.read { table2 in
if table1.isEmpty {
ModelA.save(recordToSave: [(a: 1, b: "a"), (a: 2, b: "b"), (a: 3, b: "c")]) {
ModelB.save(recordToSave: [(a: 4, b: 5.0, c: true), (a: 6, b: 7.0, c: false)]) {
self.tvReload()
}
}
} else {
self.tvReload()
}
}
}
}
var fetchedResultsControllerForModelA = CoreDataFunctions.fetchedResultsController
var fetchedResultsControllerForModelB = CoreDataFunctions.fetchedResultsController
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
tvReload()
}
func modelOfTableA(indexPath: IndexPath) -> (forLabel1: String, forLabel2: String, forLabel3: String)? {
if let fetchedResultsControllerForModelA = CoreDataFunctions.getNSManagedObjectForIndexPathOfTable(fetchedResultsController: fetchedResultsControllerForModelA, indexPath: indexPath) {
if let model = ModelA.read(nsmanagedobject: fetchedResultsControllerForModelA) {
return (forLabel1: "\(model.a)", forLabel2: model.b, forLabel3: "")
}
}
return nil
}
func modelOfTableB(indexPath: IndexPath) -> (forLabel1: String, forLabel2: String, forLabel3: String)? {
if let fetchedResultsControllerForModelB = CoreDataFunctions.getNSManagedObjectForIndexPathOfTable(fetchedResultsController: fetchedResultsControllerForModelB, indexPath: indexPath) {
if let model = ModelB.read(nsmanagedobject: fetchedResultsControllerForModelB) {
return (forLabel1: "\(model.a)", forLabel2: "\(model.b)", forLabel3: "\(model.c)")
}
}
return nil
}
func tvReload() {
fetchedResultsControllerForModelA = CoreDataFunctions(tableName: .a).fetchedResultsController(keyForSort: ModelA.a.rawValue, searchParameters: nil)
fetchedResultsControllerForModelB = CoreDataFunctions(tableName: .b).fetchedResultsController(keyForSort: ModelB.a.rawValue, searchParameters: nil)
do {
try fetchedResultsControllerForModelA?.performFetch()
try fetchedResultsControllerForModelB?.performFetch()
DispatchQueue.main.async {
self.tv.reloadData()
}
} catch {
print("Error")
}
}
func numberOfSectionsInTableView(_ tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if let sections1 = fetchedResultsControllerForModelA?.sections {
if let sections2 = fetchedResultsControllerForModelB?.sections {
return sections1[section].numberOfObjects + sections2[section].numberOfObjects
}
return sections1[section].numberOfObjects
}
return 0
}
func tableView(_ tableView: UITableView, cellForRowAtIndexPath indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
if indexPath.section == 0 {
if let modelOfTable = modelOfTableA(indexPath: indexPath) {
cell.l1.text = modelOfTable.forLabel1
cell.l2.text = modelOfTable.forLabel2
cell.l3.text = modelOfTable.forLabel3
}
} else {
if let modelOfTable = modelOfTableB(indexPath: indexPath) {
cell.l1.text = modelOfTable.forLabel1
cell.l2.text = modelOfTable.forLabel2
cell.l3.text = modelOfTable.forLabel3
}
}
return cell
}
}
I could not find any tutorial on this theme, so I am asking question there. I do not want to use inheritance from single entity in Core Data, because, in real life it would be impossible.
Thank you for any help or advice!

Answer 1

OK - I downloaded your code, and there are a couple issues...
1) If you want your data to fill two sections in the table, the table must have two sections - currently, you are just returning 1, so use this (although you may want/need different handling based on data retrieved):
func numberOfSectionsInTableView(_ tableView: UITableView) -> Int {
if fetchedResultsControllerForModelA == nil || fetchedResultsControllerForModelB == nil {
return 0
}
return 2
}
2) For number of rows in each section, your code was close but not quite right...
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if section == 0 {
if let sections = fetchedResultsControllerForModelA?.sections {
return sections[0].numberOfObjects
}
} else {
if let sections = fetchedResultsControllerForModelB?.sections {
return sections[0].numberOfObjects
}
}
return 0
}
3) For the actual cellForRowAtIndexPath data, again your code was close but you need to keep track of which data to get for each section...
func tableView(_ tableView: UITableView, cellForRowAtIndexPath indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
if indexPath.section == 0 {
if let modelOfTable = modelOfTableA(indexPath: indexPath) {
cell.l1.text = modelOfTable.forLabel1
cell.l2.text = modelOfTable.forLabel2
cell.l3.text = modelOfTable.forLabel3
}
} else {
// Each "Table data model" has only one section... since this is the 2nd table section, we need
// to change the section of the index path for our call to the data model
let dataIndexPath = IndexPath(row: indexPath.row, section: 0)
if let modelOfTable = modelOfTableB(indexPath: dataIndexPath) {
cell.l1.text = modelOfTable.forLabel1
cell.l2.text = modelOfTable.forLabel2
cell.l3.text = modelOfTable.forLabel3
}
}
return cell
}
That should get you on your way.