Swift: How to fetch Relationship Core Data by Month - swift

Question

I'm new to Swift and need your help.
I have two View Controllers with a tableview and two Entities called Groups and Singlegroups with an one to many relationship.The Entity Singlegroups has an attribute from type Date.
In View Controller 1 (MasterViewController) I show all Groups in my TableView and in the second View Controller (DetailViewController) I show all Singlegroups related to the Group of the selected row.
Now I want to load the SingleGroups on second View Controller only from current month but I can't get it to work, because I have no FetchRequest in the second View Controller. I transfer the Single Groups for the selected row in the prepareForSegue method.
I tried to call a fetchRequest manually in thousands different ways but nothing happend.
Hope you understand my problem and can help me.
MasterViewController ViewWillAppear:
import UIKit
import CoreData
class MasterViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
var groups: [Groups] = []
#IBOutlet weak var groupsTableView: UITableView!
var groupsTextField: UITextField?
override func viewDidLoad() {
super.viewDidLoad()
groupsTableView.delegate = self
groupsTableView.dataSource = self
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func viewWillAppear(_ animated: Bool) {
// Core date initialization
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext = appDelegate.persistentContainer.viewContext
let fetchRequest: NSFetchRequest<Groups> = Groups.fetchRequest()
do {
groups = try managedContext.fetch(fetchRequest)
groupsTableView.reloadData()
} catch {
// TODO: error handling
print("Could not fetch groups")
}
}
PrepareForSegue in MasterViewController:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showDetailViewController" {
guard let destination = segue.destination as? DetailViewController,
let selectedRow = self.groupsTableView.indexPathForSelectedRow?.row else {
return
}
destination.group = groups[selectedRow]
destination.title = groups[selectedRow].groupTitle
}
DetailViewController ViewWillAppear:
import UIKit
import CoreData
class DetailViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, NSFetchedResultsControllerDelegate {
var singleGroupDate: UILabel!
var singleGroupName: UILabel!
var singleGroupAmount: UILabel!
#IBOutlet weak var dateLabelTextField: UITextField!
#IBOutlet weak var singleGroupSum: UILabel!
#IBOutlet weak var singleGroupTableView: UITableView!
var groups: [Groups] = []
var group: Groups?
override func viewDidLoad() {
super.viewDidLoad()
singleGroupTableView.delegate = self
singleGroupTableView.dataSource = self
}
override func viewWillAppear(_ animated: Bool) {
// Core date initialization
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
// create alert
let alert = UIAlertController(
title: "Could not get app delegate",
message: "Could not get app delegate, unexpected error occured. Try again later.",
preferredStyle: .alert)
// add OK action
alert.addAction(UIAlertAction(title: "OK", style: .default))
// show alert
self.present(alert, animated: true)
return
}
let managedContext = appDelegate.persistentContainer.viewContext
singleGroupTableView.reloadData()
DetailViewController TableView:
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return group?.singleGroups?.count ?? 0
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = singleGroupTableView.dequeueReusableCell(withIdentifier: "SingleGroupsTableViewCell", for: indexPath) as! SingleGroupsTableViewCell
let currencyFormatter = NumberFormatter()
currencyFormatter.usesGroupingSeparator = true
currencyFormatter.numberStyle = .currency
currencyFormatter.locale = Locale.current
currencyFormatter.positivePrefix = currencyFormatter.plusSign
currencyFormatter.negativePrefix = currencyFormatter.minusSign
if let singleGroup = group?.singleGroups?[indexPath.row] {
cell.singleGroupNameLabel?.text = singleGroup.singleGroupName
cell.singleGroupAmountLabel?.text = currencyFormatter.string(from: singleGroup.singleGroupAmount as NSNumber)
cell.singleGroupAmountLabel.textColor = UIColor.red
cell.singleGroupDateLabel?.text = DateHelper.convertDate(date: singleGroup.singleGroupTimeStamp)
}
return cell
}
func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
// Return false if you do not want the specified item to be editable.
return true
}
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
deleteSingleGroup(at: indexPath)
}
}
UPDATE:
I solved it myself by writing a new fetch request for the SingleGroups Entity and changing the numbersOfRowsInSection method of my tableview.
func orderFetchRequest() -> NSFetchRequest<NSFetchRequestResult> {
let startDateFetch = Date().startOfMonth()
let endDateFetch = Date().endOfMonth()
self.startDate = startDateFetch!
self.endDate = endDateFetch!
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "SingleGroups")
let sortDescriptor = NSSortDescriptor(key: "singleGroupTimeStamp", ascending: false)
let predicate1 = NSPredicate(format: "group == %#", group!)
let predicate2 = NSPredicate(format: "singleGroupTimeStamp >= %# AND singleGroupTimeStamp <= %#", startDate as CVarArg, endDate as CVarArg)
let compound = NSCompoundPredicate(andPredicateWithSubpredicates: [predicate1, predicate2])
fetchRequest.sortDescriptors = [sortDescriptor]
fetchRequest.predicate = compound
return fetchRequest
}
func fetchData() {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
let fetchRequest = orderFetchRequest()
fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: managedContext, sectionNameKeyPath:nil, cacheName: nil)
do {
try fetchedResultsController.performFetch()
singleGroupTableView.reloadData()
}
catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
}
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return fetchedResultsController.fetchedObjects?.count ?? 0