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Accepted
Manngo
Asked: 2024-11-05 10:16:43 +0800 CST

插入到 SwiftData

  • 772

我正在尝试编写一些代码，如果新项目尚不存在，则将其插入 SwiftData。我收到了ModelContext无法解决的错误。

以下代码是精简版，足以生成错误。我删除了测试现有项目的逻辑，直到我能解决这个问题。

抱歉，太长了：

import SwiftUI
import SwiftData

@Model
class TestData {
    @Attribute(.unique) var id: String
    var value: String
    init(id: String, value: String) {
        self.id = id
        self.value = value
    }
}

struct EditTestItem: View {
    @Bindable var testData: TestData
    var body: some View {
        VStack {
            HStack {
                Text($testData.id)
                TextField("Enter Data Here", text: $testData.value)
            }
        }
        .modelContainer(for: TestData.self)
    }
}

struct TestContent: View {
    var testIDValue: String = ""
    @Environment(\.modelContext) private var modelContext
    @Query var testData: [TestData]
    var testItem: TestData
        
    init(testID: String) {
        testItem = TestData(id: testID, value: "New value: \(testID)")

        let _ = modelContext.insert(testItem)
                    
        do {
            try modelContext.save()
        } catch {
            print("\(#line) oops")
        }
    }
        
    var body: some View {
        VStack {
            VStack {
                Text(testIDValue)
                Text("\(testData.count)")
                EditTestItem(testData: testItem)
            }
            Button("Save", action: {
                try? modelContext.save()
            })
        }
        .modelContainer(for: TestData.self)
        .onAppear {

        }
    }
}

#Preview {
    TestContent(testID: "b")
        .modelContainer(for: TestData.self)
        .frame(width: 400)
}

错误包括：

访问安装在视图之外的环境值。这将始终读取默认值并且不会更新。

和

在视图环境中设置 .modelContext 以使用查询

这肯定不是添加数据。

正确的做法是什么？

swiftui

2 个回答

  1. Best Answer

    我将在 中创建测试对象，onAppear而不是使用init。

    为了清楚起见，我们将所有相关代码放在一个函数中，该函数检查是否存在现有对象，如果不存在则创建一个新对象。

    private func load(with id: String) -> TestData? {
    do {
        var object = try modelContext.fetch(FetchDescriptor<TestData>(predicate: #Predicate { $0.id == id })).first

        if object == nil {
            object = TestData(id: id, value: "New value: \(id)")
            modelContext.insert(object!)
            try modelContext.save()
        }

        return object
    } catch {
        print(error)
        return nil
    }
}

    然后我们需要对视图做一些更改来保存 id 和对象并调用新函数

    struct TestContent: View {
    let testID: String
    @Environment(\.modelContext) private var modelContext
    @Query var testData: [TestData]
    @State var testItem: TestData?

    init(testID: String) {
        self.testID = testID
    }

    var body: some View {
        VStack {
            VStack {
                // other components...
                if let testItem {
                    EditTestItem(testData: testItem)
                }
            }
            Button("Save", action: {
                try? modelContext.save()
            })
        }
        .onAppear {
            testItem = load(with: testID)
        }
    }

    private func load(with id: String) -> TestData? {
        // as above
    }
}
    • 2

  2. 这是适合我并可用于TestData测试的测试代码。

    struct ContentView: View {
    let testID: String = String(UUID().uuidString.prefix(5))
    
    var body: some View {
        TestContent(testID: testID)
    }
}

struct TestContent: View {
    @Environment(\.modelContext) private var modelContext
    @Query var testData: [TestData]
    
    var testIDValue: String = ""
    var testItem: TestData
        
    init(testID: String) {
        self.testItem = TestData(id: testID, value: "New value: \(testID)")
    }
        
    var body: some View {
        VStack {
            VStack {
                Text(testIDValue)
                Text("\(testData.count)")
                EditTestItem(testData: testItem)
            }
            Button("Save", action: {
                do {
                    try modelContext.save()
                } catch {
                    print("\(#line) oops")
                }
            })
            List {
                ForEach(testData){ test in
                    HStack {
                        Text(test.id)
                        Spacer()
                        Text(test.value)
                    }
                }
            }
        }
        
        // .task {
        .onAppear {
            modelContext.insert(testItem)
            do {
                try modelContext.save()
            } catch {
                print("\(#line) oops")
            }
        }
    }
}
 
struct EditTestItem: View {
    @Bindable var testData: TestData
    
    var body: some View {
        VStack {
            HStack {
                Text(testData.id)
                TextField("Enter Data Here", text: $testData.value)
                    .border(.red)
            }
        }
    }
}


@main
struct TestApp: App {
    var sharedModelContainer: ModelContainer = {
        let schema = Schema([
            TestData.self
        ])
        let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)

        do {
            return try ModelContainer(for: schema, configurations: [modelConfiguration])
        } catch {
            fatalError("Could not create ModelContainer: \(error)")
        }
    }()

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .modelContainer(sharedModelContainer)
    }
}
    • 1

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