xcode 无法在MVVM类中获取SwiftData ModelContainer和ModelContext的引用

46qrfjad  于 2023-06-24  发布在  Swift
关注(0)|答案(2)|浏览(125)

我正在尝试理解新的SwiftData框架。只要我在SwiftUI视图中做所有事情,让它工作起来就很容易。我试图成为一名优秀的编码员,并将数据与UI分离,但无法连接到ModelContainer,而ModelContext是一个类文件。
下面是一个可以按原样运行的示例:
型号:

@Model
final public class Thing: Identifiable {

    let myID = UUID()
    var name: String
    var comment: String

    init(name: String, comment: String) {
        self.name = name
        self.comment = comment
    }

}//struct

ContentView:将按钮中的代码更改为Create 10 Test Records以使用VM版本。

struct ContentView: View {

    @StateObject var contentVM = ContentViewModel()
    @Environment(\.modelContext) private var context

    @State private var name: String = ""
    @State private var comment: String = ""

    @State private var selection: Thing?

    @Query(sort: \.name) var things: [Thing]

    var body: some View {
        NavigationStack {
            VStack(alignment: .leading) {
                Text("Name:")
                    .padding(.leading, 12)
                TextField("name", text: $name)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    .padding(EdgeInsets(top: 5, leading: 10, bottom: 0, trailing: 10))
            
                Text("Comment:")
                    .padding(.leading, 12)
                TextField("comment", text: $comment)
                    .textFieldStyle(RoundedBorderTextFieldStyle())
                    .padding(EdgeInsets(top: 5, leading: 10, bottom: 0, trailing: 10))
            }//v
            .padding()
            VStack(spacing: 20) {
                    Button(action: {
                        let thing = Thing(name: name, comment: comment)
                        context.insert(object: thing)
                    }, label: {
                        Text("Save")
                    })
                
                    Button(action: {
                        //contentVM.createThingsForTestVM(count: 10)
                        createThingsForTest(count: 10)
                    }, label: {
                        Text("Create 10 Test Records")
                    })
                }//v buttons

            Divider()
        
            List {
                ForEach(things) { thing in
                    Text(thing.name)
                }
                .onDelete(perform: deleteThings(at:))
            }//list
            .toolbar {
                ToolbarItemGroup(placement: .navigationBarTrailing) {
                    Button {
                        deleteAllThings()
                    } label: {
                        Image(systemName: "trash")
                    }

                }//group
            }//toolbar
        }//nav stack
    }//body

    private func deleteThings(at offsets: IndexSet) {
        withAnimation {
            offsets.map { things[$0] }.forEach(deleteThing)
        }
    }//delete at offsets

    private func deleteThing(_ thing: Thing) {

        //Unselect the item before deleting it.
        if thing.objectID == selection?.objectID {
            selection = nil
        }
        context.delete(thing)
    }//delete things

    private func deleteAllThings() {
    
        for t in things {
            if t.objectID == selection?.objectID {
                selection = nil
            }
            context.delete(t)
        }
    }//delete all things

    private func createThingsForTest(count: Int) {
    
        for i in 0..<count {
            let t = Thing(name: "Name " + String(i), comment: "Comment " + String(i))
            context.insert(object: t)
        }
    
        do {
            try context.save()
        } catch {
            print(error)
        }
    
    }//create things

}//struct content view

ContentViewModel:这确实会创建记录,但它不会更新UI,对我来说这似乎是错误的方法。我试图在初始化器中设置ModelContainer和ModelContext,但根本无法实现。

class ContentViewModel: ObservableObject {

    init() {}

    @MainActor
    func createThingsForTestVM(count: Int) {
    
        do {
            let container = try ModelContainer(for: Thing.self)
            let context = container.mainContext
        
            for i in 0..<count {
                let t = Thing(name: "Name " + String(i), comment: "Comment " + String(i))
                context.insert(object: t)
            }
        
            try context.save()
        
        } catch {
            print("Could not create a container \(error.localizedDescription)")
        }
    }//create things
}//class

任何指导将不胜感激。Xcode 15.0 Beta(15A5160n),iOS17.0

iklwldmw

iklwldmw1#

在SwiftUI中,View结构已经与UI分离,View结构层次结构应该是视图数据的主要封装机制。
SwiftUI区分这些结构,并自动为您创建/更新/删除UI对象,即它管理实际的视图层或MVC中的V。
因此,您只需移除自定义视图模型对象,并按设计使用View结构和属性 Package 器。
StateObject用于当你想要在一个State中引用类型时,比如你正在做一些异步的事情,而生命周期绑定到屏幕上的某个东西。现在我们有了async await和任务修饰符it在大多数情况下不再需要。

2skhul33

2skhul332#

我也在纠结同样的事情-我注意到一件事:
而不是:

let container = try ModelContainer(for: Thing.self)
let context = container.mainContext

尝试:

let container = try ModelContainer(for: Thing.self)
let context = ModelContext(container)

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