SwiftUI: How to show/edit an int from CoreData without being in a List? - core-data

Question

self-learning beginner here. I am trying to show an Int from Core Data in a VStack in ContentView, not in a List. But literally all the tutorials I can find about Core Data (tracking Books, Movies, Orders, Students) are using a List to show an array containing an Int. Nothing on showing an Int by itself.
Xcode can build countnum.countnum +=1 with no problem. Seems to me it is reading it fine. But once I try to show it, it just doesn’t work. I’m wrecking my brain here.
struct ContentView: View {
#Environment(\.managedObjectContext) var moc
#FetchRequest(sortDescriptors: []) var countnum: FetchedResults<CountNum>
var body: some View {
// let countnum = CountNum(context: moc)
VStack{
Text("+")
.padding()
.onTapGesture (count: 2){
let countnum = CountNum(context: moc)
countnum.countnum += 1
}
Text("\(countnum)") //No exact matches in call to instance method 'appendInterpolation'
}
}
}
Thanks

Answer 1

....all the tutorials ... show an array containing an Int. Yes, that's because CoreData
can contain many "objects". You get an array of your CountNum objects when
you do your .....var countnum: FetchedResults<CountNum>. So you need to decide which CountNum you want to
use. For example, if you want to use the first one, then:
struct ContentView: View {
#Environment(\.managedObjectContext) var moc
#FetchRequest(sortDescriptors: []) var countnum: FetchedResults<CountNum>
var body: some View {
VStack {
if let firstItem = countnum.first {
Text("+")
.padding()
.onTapGesture(count: 2) {
firstItem.countnum += 1
do {
try moc.save()
} catch {
print(error)
}
}
Text("\(firstItem.countnum)").foregroundColor(.green)
}
}
}
}
EDIT-1: adding new CountNum to CoreData example code in the add button.
struct ContentView: View {
#Environment(\.managedObjectContext) var moc
#FetchRequest(sortDescriptors: []) var countnum: FetchedResults<CountNum>
var body: some View {
Button(action: {add()}) { Text("add new CountNum").foregroundColor(.green) }
.padding(.top, 50)
List {
ForEach(countnum) { item in
HStack {
Text("++")
.onTapGesture(count: 2) { increment(item) }
Text("\(item.countnum)").foregroundColor(.blue)
Text("delete").foregroundColor(.red)
.onTapGesture { delete(item: item) }
}
}
}
}
func increment(_ item: CountNum) {
item.countnum += 1
save()
}
func add() {
let countnum = CountNum(context: moc)
countnum.countnum = 0
save()
}
func delete(item: CountNum) {
moc.delete(item)
save()
}
func save() {
do { try moc.save() } catch { print(error) }
}
}