SwifUI: How to get manual list to refresh when updating CoreData records? - core-data

Question

I have a CoreData table that has several repeated records that don't need to be stored but do need to be displayed in my user interface. I have manually created my arrays based on the CoreData table. I have made them Observable Objects so they should automatically update and I have made them Hashable and Equatable.
My problem is that the list does not update when the database records are updated. This works fine when records are being added.
Here is my much simplified code in full that demonstrates the problem:
import SwiftUI
let persistentContainerQueue = OperationQueue()
let firstNames = ["Michael", "Damon", "Jacques", "Mika", "Fernando", "Kimi", "Lewis", "Jenson", "Sebastion", "Nico"]
let lastNames = ["Schumacher", "Hill", "Villeneuve", "Hakkinen", "Alonso", "Raikkonen", "Hamilton", "Button", "Vettel", "Rosberg"]
class RepeatedPerson: ObservableObject, Hashable
{
#Published var person: Person
#Published var index: Int
#Published var tested: Bool
init (person: Person, index: Int, tested: Bool)
{
self.person = person
self.index = index
self.tested = tested
}
func hash(into hasher: inout Hasher)
{
hasher.combine(person.firstName)
hasher.combine(person.lastName)
hasher.combine(index)
}
static func == (lhs: RepeatedPerson, rhs: RepeatedPerson) -> Bool
{
return lhs.person.firstName == rhs.person.firstName &&
lhs.person.lastName == rhs.person.lastName &&
lhs.index == rhs.index
}
}
class RepeatedPeople: ObservableObject
{
#Published var people: [RepeatedPerson] = []
}
func getRepeatedPeople() -> [RepeatedPerson]
{
var repeatedPeople:[RepeatedPerson] = []
let records = allRecords(Person.self)
for person in records
{
for index in 1...3
{
repeatedPeople.append(RepeatedPerson(person: person, index: index, tested: true))
}
}
return repeatedPeople
}
struct ContentView: View
{
#Environment(\.managedObjectContext) private var viewContext
#ObservedObject var repeatedPeople = RepeatedPeople()
init()
{
repeatedPeople.people = getRepeatedPeople()
}
var body: some View
{
VStack
{
List()
{
ForEach(repeatedPeople.people, id: \.self)
{ repeatedPerson in
Text("\(repeatedPerson.index)) \(repeatedPerson.person.firstName!) \(repeatedPerson.person.lastName!)")
}
}
HStack
{
Button("Add Record", action:
{
addItem()
repeatedPeople.people = getRepeatedPeople()
})
Button("Change Record", action:
{
let q = allRecords(Person.self)
let oldLastName = q[0].lastName
q[0].lastName = lastNames.randomElement()!
print ("changed \(q[0].firstName!) \(oldLastName!) -> \(q[0].firstName!) \(q[0].lastName!)")
saveDatabase()
})
Button("Reset Database", action:
{
deleteAllRecords(Person.self)
})
}
}
}
private func addItem()
{
withAnimation
{
let newItem = Person(context: viewContext)
newItem.timestamp = Date()
newItem.firstName = firstNames.randomElement()!
newItem.lastName = lastNames.randomElement()!
print ("added \(newItem.firstName!) \(newItem.lastName!)")
saveDatabase()
}
}
}
func allRecords<T: NSManagedObject>(_ type : T.Type, sort: NSSortDescriptor? = nil) -> [T]
{
let context = PersistenceController.shared.container.viewContext
let request = T.fetchRequest()
if let sortDescriptor = sort
{
request.sortDescriptors = [sortDescriptor]
}
do
{
let results = try context.fetch(request)
return results as! [T]
}
catch
{
print("Error with request: \(error)")
return []
}
}
func deleteAllRecords<T: NSManagedObject>(_ type : T.Type)
{
let context = PersistenceController.shared.container.viewContext
let results = allRecords(T.self)
for record in results
{
context.delete(record as NSManagedObject)
}
saveDatabase()
}
func saveDatabase()
{
persistentContainerQueue.addOperation()
{
let context = PersistenceController.shared.container.viewContext
context.performAndWait
{
try? context.save()
}
}
}
To reproduce the problem, add a few records. These will be shown in the list. Then click the 'Update Record' button. The CoreData record will be updated (you can see this the next time you run the app) but the changes will not be shown.
How do I get the new changes to show?
If you add another record the changes will then be shown. A side effect is that the list introduces wild spaces between the records. I have seen this is in other places. Is this a SwiftUI bug?

Answer 1

OK it turned out to be really quite simple. All I actually had to do was remove some of the #Published and provide a UUID for the repeatedPerson record (and for == and hash).
import SwiftUI
import CoreData
let persistentContainerQueue = OperationQueue()
let firstNames = ["Michael", "Damon", "Jacques", "Mika", "Fernando", "Kimi", "Lewis", "Jenson", "Sebastion", "Nico"]
let lastNames = ["Schumacher", "Hill", "Villeneuve", "Hakkinen", "Alonso", "Raikkonen", "Hamilton", "Button", "Vettel", "Rosberg"]
class RepeatedPerson: ObservableObject, Hashable
{
var id: UUID = UUID()
var index: Int
var person: Person?
init (person: Person, index: Int)
{
self.person = person
self.index = index
}
func hash(into hasher: inout Hasher)
{
hasher.combine(id)
}
static func == (lhs: RepeatedPerson, rhs: RepeatedPerson) -> Bool
{
return lhs.id == rhs.id
}
}
class RepeatedPeople: ObservableObject
{
#Published var people: [RepeatedPerson] = []
}
func getRepeatedPeople() -> [RepeatedPerson]
{
var repeatedPeople:[RepeatedPerson] = []
let records = allRecords(Person.self)
for person in records
{
for index in 1...3
{
repeatedPeople.append(RepeatedPerson(person: person, index: index))
}
}
return repeatedPeople
}
struct ContentView: View
{
#Environment(\.managedObjectContext) private var viewContext
#ObservedObject var repeatedPeople = RepeatedPeople()
init()
{
repeatedPeople.people = getRepeatedPeople()
}
var body: some View
{
VStack
{
List()
{
ForEach(repeatedPeople.people, id: \.self)
{ repeatedPerson in
Text("\(repeatedPerson.index)) \(repeatedPerson.person!.firstName!) \(repeatedPerson.person!.lastName!)")
}
}
HStack
{
Button("Add Record", action:
{
addItem()
repeatedPeople.people = getRepeatedPeople()
})
Button("Change Record", action:
{
let q = allRecords(Person.self)
let r = q.randomElement()!
let oldLastName = r.lastName
r.lastName = lastNames.randomElement()!
print ("changed \(r.firstName!) \(oldLastName!) -> \(r.firstName!) \(r.lastName!)")
saveDatabase()
repeatedPeople.people = getRepeatedPeople()
})
Button("Reset Database", action:
{
print ("Reset database")
deleteAllRecords(Person.self)
repeatedPeople.people = getRepeatedPeople()
})
}
}
}
private func addItem()
{
withAnimation
{
let newItem = Person(context: viewContext)
newItem.timestamp = Date()
newItem.firstName = firstNames.randomElement()!
newItem.lastName = lastNames.randomElement()!
print ("added \(newItem.firstName!) \(newItem.lastName!)")
saveDatabase()
}
}
}
func query<T: NSManagedObject>(_ type : T.Type, predicate: NSPredicate? = nil, sort: NSSortDescriptor? = nil) -> [T]
{
let context = PersistenceController.shared.container.viewContext
let request = T.fetchRequest()
if let sortDescriptor = sort
{
request.sortDescriptors = [sortDescriptor]
}
if let predicate = predicate
{
request.predicate = predicate
}
do
{
let results = try context.fetch(request)
return results as! [T]
}
catch
{
print("Error with request: \(error)")
return []
}
}
func allRecords<T: NSManagedObject>(_ type : T.Type, sort: NSSortDescriptor? = nil) -> [T]
{
return query(T.self, sort: sort)
}
func deleteAllRecords<T: NSManagedObject>(_ type : T.Type)
{
let context = PersistenceController.shared.container.viewContext
let results = allRecords(T.self)
for record in results
{
context.delete(record as NSManagedObject)
}
saveDatabase()
}
func saveDatabase()
{
persistentContainerQueue.addOperation()
{
let context = PersistenceController.shared.container.viewContext
context.performAndWait
{
try? context.save()
}
}
}