Core data not triggering immediate refresh with SwiftUI - core-data

Question

I'm at a loss with this problem I've been troubleshooting the past few days.
I am drawing a custom shape, and the user can move one of the points around via a drag gesture. I want the shape to redraw, live, when moving the point around.
Here is some sample code that is working using CGPoint.
import SwiftUI
struct ShapeTest: Shape {
#State var points: [CGPoint]
#State var closed: Bool = true
func path(in rect: CGRect) -> Path {
var path = Path()
if (points.count > 0) {
path.move(to: points.first!)
path.addLines(points)
if closed { path.closeSubpath() }
}
return path
}
}
struct RedrawEdgeTestCGPoint: View {
#State var points = [CGPoint]()
#State var originalPosition: CGPoint? = nil
private var movePointDragGesture: some Gesture {
DragGesture(minimumDistance: 0, coordinateSpace: .local)
.onChanged { value in
if points.isEmpty {
return
}
if originalPosition == nil {
originalPosition = CGPoint(x: points.last!.x, y: points.last!.y)
}
let lastIndex = points.count - 1
points[lastIndex].x = originalPosition!.x + value.translation.width
points[lastIndex].y = originalPosition!.y + value.translation.height
}
.onEnded { value in
originalPosition = nil
}
}
private var addNewPointGesture: some Gesture {
TapGesture(count: 2)
.onEnded {
points.append(CGPoint())
}
}
var body: some View {
GeometryReader { geometry in
Group {
ShapeTest(points: points)
.stroke()
}
.contentShape(Rectangle())
.gesture(movePointDragGesture.simultaneously(with: addNewPointGesture))
}
}
}
struct RedrawEdgeTestCGPoint_Previews: PreviewProvider {
static var previews: some View {
RedrawEdgeTestCGPoint()
}
}
Now, here is another code sample. This example is generally the same thing, but this is using a Point entity I've defined in Core Data instead of CGPoint.
import SwiftUI
struct RedrawEdgeTestCoreData: View {
#Environment(\.managedObjectContext) private var viewContext
#State var points: [Point] = []
#State var originalPosition: CGPoint? = nil
private var movePointDragGesture: some Gesture {
DragGesture(minimumDistance: 0, coordinateSpace: .local)
.onChanged { value in
if points.isEmpty {
return
}
if originalPosition == nil {
originalPosition = CGPoint(x: points.last!.x, y: points.last!.y)
}
let lastIndex = points.count - 1
points[lastIndex].x = originalPosition!.x + value.translation.width
points[lastIndex].y = originalPosition!.y + value.translation.height
}
.onEnded { value in
originalPosition = nil
}
}
private var addNewPointGesture: some Gesture {
TapGesture(count: 2)
.onEnded {
points.append(Point(context: viewContext))
}
}
var body: some View {
GeometryReader { geometry in
Group {
ShapeTest(points: points.map { CGPoint(x: $0.x, y: $0.y) })
.stroke()
}
.contentShape(Rectangle())
.gesture(movePointDragGesture.simultaneously(with: addNewPointGesture))
}
}
}
struct RedrawEdgeTestCoreData_Previews: PreviewProvider {
static var previews: some View {
RedrawEdgeTestCoreData()
.environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
The version utilizing Core Data does not update while dragging. It will redraw when I double tap to add another point.
Any suggestions as to why this is happening?

Answer 1

I used the approach suggested by jnpdx and it works.
import SwiftUI
class PointsViewModel: ObservableObject {
#Published var points = [Point]()
func movePoint(index: Int, x: CGFloat, y: CGFloat) {
points[index].x = x
points[index].y = y
objectWillChange.send()
}
}
struct RedrawEdgeTestCoreData: View {
#Environment(\.managedObjectContext) private var viewContext
#ObservedObject var viewModel: PointsViewModel
#State var originalPosition: CGPoint? = nil
private var movePointDragGesture: some Gesture {
DragGesture(minimumDistance: 0, coordinateSpace: .local)
.onChanged { value in
if viewModel.points.isEmpty {
return
}
if originalPosition == nil {
originalPosition = CGPoint(x: viewModel.points.last!.x, y: viewModel.points.last!.y)
}
let lastIndex = viewModel.points.count - 1
viewModel.movePoint(index: lastIndex, x: originalPosition!.x + value.translation.width, y: originalPosition!.y + value.translation.height)
}
.onEnded { value in
originalPosition = nil
}
}
private var addNewPointGesture: some Gesture {
TapGesture(count: 2)
.onEnded {
viewModel.points.append(Point(context: viewContext))
}
}
var body: some View {
GeometryReader { geometry in
ZStack {
ShapeTest(points: viewModel.points.map { CGPoint(x: $0.x, y: $0.y) })
.stroke()
}
.contentShape(Rectangle())
.gesture(movePointDragGesture.simultaneously(with: addNewPointGesture))
}
}
}
struct RedrawEdgeTestCoreData_Previews: PreviewProvider {
static var previews: some View {
RedrawEdgeTestCoreData(viewModel: PointsViewModel())
.environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}