初始化核心数据 SwiftUI

我正在尝试初始化数据，以便当用户第一次安装应用程序时它会有一些数据。 init 不起作用，但为什么呢？

对于核心数据上的 CRUD 操作，我正在使用xcdatamodeld包含名为的实体的文件ProgrammingLanguage它有两个字符串属性：“name”和“creator”。这是代码：

struct ContentView: View {

@Environment(\.managedObjectContext) var managedObjectContext

@FetchRequest(
    entity: ProgrammingLanguage.entity(),
    sortDescriptors: [
        NSSortDescriptor(keyPath: \ProgrammingLanguage.name, ascending: true),
    ]
) var languages: FetchedResults<ProgrammingLanguage>

init() {

    let language = ProgrammingLanguage(context: self.managedObjectContext)
    language.name = "SwiftUI"
    language.creator = "Some text"

    do {
        try self.managedObjectContext.save()
    } catch {
    }

}

var body: some View {
    NavigationView {
        List {
            ForEach(languages, id: \.self) { language in
                Button(action: {
                }) {
                    Text("Creator: \(language.creator ?? "Anonymous")")
                }

            }
        }
    }
}
}

就好像它没有保存它一样。这里发生了什么？该 init 应该在数据库上创建数据，我将能够在视图上读取它......

SwiftUI

我建议这样做.onAppear()修饰符。在您的代码示例中它将是：

struct ContentView: View {
    
    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(
        entity: ProgrammingLanguage.entity(),
        sortDescriptors: [
            NSSortDescriptor(keyPath: \ProgrammingLanguage.name, ascending: true),
        ]
    ) var languages: FetchedResults<ProgrammingLanguage>
    
    
    var body: some View {
        NavigationView {
            List {
                ForEach(languages, id: \.self) { language in
                    Button(action: {
                    }) {
                        Text("Creator: \(language.creator ?? "Anonymous")")
                    }
                    
                }
            }.onAppear() {
                let language = ProgrammingLanguage(context: self.managedObjectContext)
                language.name = "SwiftUI"
                language.creator = "Some text"
                do {
                    try self.managedObjectContext.save()
                } catch let error {
                    print(error)
                }
            }
        }
    }
}

希望这会有所帮助！ 我在这里找到了解决方案：苹果开发者论坛 https://developer.apple.com/forums/thread/132746