SwiftUI与Core Data问题：发布器失效，上下文未检测到变更

Hey there, let's break down your issues one by one and work through practical solutions for both your Core Data synchronization problems and UI glitches.

Core Data Custom Class Sync & View Update Issues #

The root problem here is twofold:

1. Core Data’s Transformable properties only detect changes when the object reference itself changes—internal property updates in your custom Nodes/Node classes don’t trigger Core Data to mark the parent Record as dirty.
2. Your @Published modifiers notify SwiftUI of changes, but this doesn’t automatically sync back to the Core Data context, so changes aren’t persisted or propagated to other parts of your app.

Option 1: Fix Your Current Custom Class Structure #

To make this work without rewriting your data model, add NSCopying conformance to your classes so you can trigger Core Data’s change detection when internal properties update:

1. Update Node to conform to NSCopying:

extension Node: NSCopying {
    public func copy(with zone: NSZone? = nil) -> Any {
        let copiedNode = Node(x: self.xString, y: self.yString)
        copiedNode.id = self.id // Preserve the ID for consistency
        return copiedNode
    }
}

2. Update Nodes to conform to NSCopying and add a weak reference to its parent Record:

@objc(Nodes)
public class Nodes: NSObject, NSSecureCoding, ObservableObject {
    public static var supportsSecureCoding: Bool = true
    @Published public var nodes = [Node]()
    weak var parentRecord: Record? // Add this to link to the parent Core Data object
    
    // ... existing init/encoding code ...
    
    func didUpdateNode(node: Node) {
        // Create a copy of Nodes to trigger Core Data change detection
        guard let record = parentRecord else { return }
        let copiedNodes = self.copy() as! Nodes
        record.nodes = copiedNodes // Replace the old reference with the copy
        
        // Notify SwiftUI and save the context
        objectWillChange.send()
        try? record.managedObjectContext?.save()
    }
}

extension Nodes: NSCopying {
    public func copy(with zone: NSZone? = nil) -> Any {
        let copiedNodes = Nodes(nodes: self.nodes.map { $0.copy() as! Node })
        copiedNodes.parentRecord = self.parentRecord
        return copiedNodes
    }
}

3. When initializing Nodes for a Record, set the parentRecord property:

// In your Record setup code
let newNodes = Nodes(nodes: [Node(x: 0, y: 0)])
newNodes.parentRecord = record
record.nodes = newNodes

Option 2: Refactor to Core Data Entities (Long-Term Solution) #

For better maintainability, replace your custom classes with Core Data entities—this is the idiomatic way to handle nested data in Core Data:

• Create a Node entity with x and y string attributes
• Add a one-to-many relationship from Record to Node (name it nodes)
• Delete your custom Nodes class entirely; use Core Data’s built-in relationship management

This way, any change to a Node’s properties will automatically mark the context as dirty, and SwiftUI will update via @FetchRequest or @ObservedObject without manual copy logic.

UI Glitch: Unresponsive Taps & Delayed Detail Views #

This is almost always caused by gesture conflicts or misconfigured NavigationLink setups. Try these fixes:

1. Avoid nesting NavigationLink inside a Button
   Use NavigationLink directly as the root of your RecordThumbnailView instead of wrapping it in a button:

struct RecordThumbnailView: View {
    let record: Record
    
    var body: some View {
        NavigationLink(destination: RecordDetailView(record: record)) {
            // Your thumbnail content (e.g., image, title)
            VStack {
                Image(systemName: "chart.bar")
                Text(record.title ?? "Untitled")
            }
            .frame(width: 120, height: 120)
            .background(Color.gray.opacity(0.2))
            .cornerRadius(8)
        }
    }
}

2. Fix isActive binding issues (if using programmatic navigation)
   If you’re using isActive to trigger navigation, ensure you reset the binding when the detail view dismisses:

struct ContentView: View {
    @FetchRequest(sortDescriptors: []) private var records: FetchedResults<Record>
    @State private var selectedRecord: Record?
    
    var body: some View {
        List(records) { record in
            Button(action: { selectedRecord = record }) {
                RecordThumbnailView(record: record)
            }
        }
        .background(
            NavigationLink(
                destination: selectedRecord.map { RecordDetailView(record: $0) } ?? EmptyView(),
                tag: selectedRecord,
                selection: $selectedRecord
            ) { EmptyView() }
        )
    }
}

UI Glitch: Chart View Shift Under Navigation Bar #

This happens when your chart view doesn’t respect safe area insets, especially if it uses a UIKit-backed view (like UIViewControllerRepresentable). Try these fixes:

1. Adjust safe area insets for SwiftUI views

struct ChartViewControllerView: View {
    var body: some View {
        // Your chart content here
        LineChart(data: [/* your data */])
            .navigationBarTitleDisplayMode(.inline) // Shorter navigation bar reduces overlap
            .edgesIgnoringSafeArea(.bottom) // Only ignore bottom, not top
            .padding(.top, 8) // Add small top padding if needed
    }
}

2. Fix UIKit-backed chart views
   If your chart is wrapped in UIViewControllerRepresentable, disable extended layout for the underlying view controller:

struct ChartViewControllerView: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> ChartViewController {
        let vc = ChartViewController()
        vc.edgesForExtendedLayout = .none // Prevents view from extending under navigation bar
        return vc
    }
    
    func updateUIViewController(_ uiViewController: ChartViewController, context: Context) {}
}

内容的提问来源于stack exchange，提问作者JacobCXDev