Swift:使用 self.moc.save() 保存核心数据时出现 Nil 错误 [英] Swift: Nil Error when using self.moc.save() to save in core data

问题描述

由于我将项目更改为使用objectWillChange.send()"，因此我得到了零错误.因为我需要手动更新视图，因为它不会为自定义轮播视图更新自身(因为核心数据?).

I get nil error since I changed my project to use 'objectWillChange.send()'. Because I needed to update the view manually since it doesn't update itself for custom carousel view(because of core data?).

如果我写1"然后点击下一个按钮(NavigationLink)

If I write "1" and tap the next button(NavigationLink)

控制台日志
页面名称:1
捕获错误:nilError

Console log
page.name: 1
catch error: nilError

这是代码.

AddPage 类

class AddPage: ObservableObject {
@Environment(\.presentationMode) var presentation
@Environment(\.managedObjectContext) var moc

    func addPage(item: String) {
    
        if item != "" {
        
            let page = Page(context: self.moc)
            page.name = item
        
            do {
                print("page.name: \(page.name ?? "Unknown")")
                try self.moc.save()
            } catch {
            print("catch: \(error)")
            }
        
            objectWillChange.send()
            presentation.wrappedValue.dismiss()
        }
    }
}

AddPageView

@ObservedObject var add = AddPage()  

NavigationLink(destination: ContentView()){
Text("Next")
    .background(
        Rectangle()
            .frame(width: 330, height: 60, alignment: .center)
    )
    .onTapGesture {
        add.addPage(item: pageName)
    }
}

SceneDelegate 类

added only

var addpage = AddPage()
let contentView = ContentView()
            .environment(\.managedObjectContext, context)
            .environmentObject(addpage)

有人可以帮我吗..?

推荐答案

更改

@Environment(\.managedObjectContext) var moc 

例如(如果您使用的是 Xcode 生成的示例代码)如果不是手动获取您的 moc 但是您设置了它

To something like (If you are using the sample code that Xcode generates) if not manually get your moc however you set it up

var moc = PersistentController.shared.container.viewContext

@Environment 包装器在 class 中不一致，它们只能在 SwiftUI View 中使用.

@Environment wrappers are inconsistent in a class they should only be used in a SwiftUI View.

如果您没有 PersistentController，请从具有 SwiftUI 生命周期和 CoreData 的全新项目中获取代码.小心并保留原始堆栈中的名称，它通常是应用程序名称

If you don't have a PersistentController get the code from a brand new project with SwiftUI lifecycle and CoreData. Be CAREFUL and keep the name from the original stack it is usually the app name

从SceneDelegate 和

创建一个变量

let context = PersistentController.shared.container.viewContext

所以你可以在你的 View

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