如何在 Core Data iOS Swift 中删除和更新结构类型数组? [英] How to delete and update structure type array in Core Data iOS Swift?

问题描述

如何在 Core Data iOS Sswift 中删除和更新结构类型数组?我正在像这样保存到核心数据.我需要删除和更新包含值的选定单元格

How to delete and update structure type array in Core Data iOS Sswift? I am saving to core data like this. I need to delete and update selected cell containing values

let projectsInfo = NSEntityDescription.insertNewObject(forEntityName:"ItemsInfo", into: delegate.persistentContainer.viewContext) as! ItemsInfo
let auditArray:[String:[lendingData]] = ["allcreditData":SaveWitnessData.shared.LendingDataArray]
let jsonData = try! JSONEncoder().encode(auditArray) projectsInfo.values = jsonData
delegate.saveContext()

我的结构就像

struct lendingData : Codable {
    let userName : String
    let amount : String
    let date : String
    let type : String
    var witnessDetails : [witnessData]
}

推荐答案

选项 1.

使用 class 和 NSSecureCoding 是最好的方法.最灵活.

Using a class and NSSecureCoding is the best way of doing this. The most flexible.

///To See the whole thing in action you have to follow a few steps
///Step 1. Create an new SwiftUI project with CoreData
///Step 2. Copy all the code in Option 1 into a `.swift` file
///Step 3. Go to the `Persistence.swift` file
///         Place these 2 lines
///            `WitnessDataTransformer.register()`
///            `LendingDataTransformer.register()`
///         Just under `container = NSPersistentCloudKitContainer(name: "YourAppName")
///Step 4. Go to the CoreData model
///         Select the `Item` Entity
///         Add a `lendingData` attribute of type `Transformable`
///         Update the `Transformer` and `Custom Class` in the `Data Model Inspector` as shown
///Step 5. You should see the View on Canvas in this point

第 4 步的照片

代码

import SwiftUI
//struct and class should start with an uppercase
//You need secureCoding not codable
//You have to change to class because NSSecurecoding is not available for a struct -https://developer.apple.com/documentation/foundation/nssecurecoding
public class LendingData : NSObject, Identifiable, ObservableObject{
    public let id: String
    @Published var userName : String
    @Published var amount : String
    @Published var date : String
    @Published var type : String
    //WitnessData needs to conform to secure coding as well
    @Published var witnessDetails : [WitnessData]

    static func sample() -> LendingData {
        LendingData(id: UUID().uuidString, userName: "sample name", amount: "10.00", date: "(Date())", type: "sample type", witnessDetails: [WitnessData.sample(), WitnessData.sample()])
    }
    static func blank() -> LendingData {
        LendingData(id: UUID().uuidString, userName: "", amount: "", date: "", type: "", witnessDetails: [])
    }
    public enum CodingKeys: String, CodingKey {
        case id
        case userName
        case amount
        case date
        case type
        case witnessDetails
    }
    public init(id: String, userName : String, amount : String, date : String, type : String, witnessDetails : [WitnessData]) {
        self.id = id
        self.userName = userName
        self.amount = amount
        self.date = date
        self.type = type
        self.witnessDetails = witnessDetails
    }
    public required init?(coder: NSCoder) {
        id = coder.decodeObject(forKey: CodingKeys.id.rawValue) as! String
        userName = coder.decodeObject(forKey: CodingKeys.userName.rawValue) as! String
        amount = coder.decodeObject(forKey: CodingKeys.amount.rawValue) as! String
        date = coder.decodeObject(forKey: CodingKeys.date.rawValue) as! String
        type = coder.decodeObject(forKey: CodingKeys.type.rawValue) as! String
        witnessDetails = coder.decodeArrayOfObjects(ofClass: WitnessData.self, forKey: CodingKeys.witnessDetails.rawValue)  ?? []
    }
}
extension LendingData: NSSecureCoding{
    public static var supportsSecureCoding: Bool{
        return true
    }
    public func encode(with coder: NSCoder) {
        coder.encode(id, forKey: CodingKeys.id.rawValue)
        coder.encode(userName, forKey: CodingKeys.userName.rawValue)
        coder.encode(amount, forKey: CodingKeys.amount.rawValue)
        coder.encode(date, forKey: CodingKeys.date.rawValue)
        coder.encode(type, forKey: CodingKeys.type.rawValue)
        coder.encode(witnessDetails, forKey: CodingKeys.witnessDetails.rawValue)
    }
}
///MUST CALL LendingDataTransformer.register() right after creating the Persistent Container before setup and loading store
@objc(LendingDataTransformer)
public final class LendingDataTransformer: NSSecureUnarchiveFromDataTransformer {
    public static let name = NSValueTransformerName(rawValue: String(describing: LendingDataTransformer.self))
    public override static var allowedTopLevelClasses: [AnyClass] {
        return [LendingData.self, NSString.self, NSArray.self, WitnessData.self]
    }

    //Register before CoreData setup starts
    @objc dynamic
    public static func register() {
        let transformer = LendingDataTransformer()
        ValueTransformer.setValueTransformer(transformer, forName: name)
    }
}
//You have to change to class because NSSecurecoding is not available for a struct -https://developer.apple.com/documentation/foundation/nssecurecoding
public class WitnessData: NSObject, Identifiable, ObservableObject{
    public let id: String
    //This is just a sample since you did not provide the struct
    //Add your variables to
    //    the class,
    //    the CodingKeys,
    //    init?(coder: NSCoder),
    //    encode(with coder: NSCoder), and
    //    init(id: String, name : String).
    //  Just follow the pattern.
    @Published var name: String

    static func sample() -> WitnessData{
        WitnessData(id: UUID().uuidString, name: UUID().uuidString)
    }
    static func blank() -> WitnessData{
        WitnessData(id: UUID().uuidString, name: "")
    }
    public enum CodingKeys: String, CodingKey {
        case id
        case name
    }
    public init(id: String, name : String) {
        self.id = id
        self.name = name

    }
    public required init?(coder: NSCoder) {
        id = coder.decodeObject(forKey: CodingKeys.id.rawValue) as? String ?? ""
        name = coder.decodeObject(forKey: CodingKeys.name.rawValue) as? String ?? ""
    }
}
extension WitnessData: NSSecureCoding{
    public static var supportsSecureCoding: Bool{
        return true
    }
    public func encode(with coder: NSCoder) {
        coder.encode(id, forKey: CodingKeys.id.rawValue)
        coder.encode(name, forKey: CodingKeys.name.rawValue)
    }
}
///MUST CALL WitnessDataTransformer.register() right after creating the Persistent Container before setup and loading store
@objc(WitnessDataTransformer)
public final class WitnessDataTransformer: NSSecureUnarchiveFromDataTransformer {
    public static let name = NSValueTransformerName(rawValue: String(describing: WitnessDataTransformer.self))
    public override static var allowedTopLevelClasses: [AnyClass] {
        return [WitnessData.self, NSString.self, NSArray.self]
    }
    //Register before CoreData setup starts
    @objc dynamic
    public static func register() {

        let transformer = WitnessDataTransformer()
        ValueTransformer.setValueTransformer(transformer, forName: name)
    }
}

以下 SwiftUI 代码适用于选项 1 或选项 2

The below SwiftUI code works for both option 1 or option 2

///This is just a sample View
struct LendingDataView: View {
    //You will need the original ObservableObject if you want to be able to show changes
    //SwiftUI depends on being told that there are chagnes so it can reload Views
    @ObservedObject var item: Item
    var body: some View {
        if item.lendingData != nil{
            List{
                TextField("username",text: $item.lendingData.bound.userName)
                TextField("amount",text: $item.lendingData.bound.amount)
                TextField("date",text: $item.lendingData.bound.date)
                TextField("type",text: $item.lendingData.bound.type)
                Section(content: {
                    ForEach($item.lendingData.bound.witnessDetails, content: { $witness in
                        HStack{
                            TextField("name",text: $witness.name)
                            Spacer()
                            //For deleting by object
                            Image(systemName: "trash")
                                .foregroundColor(.red)
                                .onTapGesture {
                                    let idx = item.lendingData!.witnessDetails.firstIndex(where: {
                                        $0.id == witness.id
                                    })
                                    if idx != nil{
                                        item.lendingData!.witnessDetails.remove(at: idx!)
                                    }
                                    //Because you are so far down the line you have to tell the ObservableObject there is a change
                                    //If you dont you won't see the new items until something happens to trigger a refresh
                                    //item.objectWillChange.send()
                                    item.objectWillChange.send()
                                }
                        }
                    })
                    //For deleting by index
                        .onDelete(perform: { indexSet in
                            for idx in indexSet{
                                item.lendingData!.witnessDetails.remove(at: idx)
                            }
                        })
                }, header: {
                    HStack{
                        Text("Witness Data")
                        Button(action: {
                            item.lendingData!.witnessDetails.append(WitnessData.blank())
                            //Because you are so far down the line you have to tell the ObservableObject there is a change
                            //If you dont you won't see the new items until something happens to trigger a refresh
                            item.objectWillChange.send()
                        }, label: {
                            Image(systemName: "plus")
                        })
                    }
                })
            }
        }else{
            VStack{
                Text("no lending data")
                Button(action: {
                    item.lendingData = LendingData.blank()
                }, label: {
                    Image(systemName: "plus")
                })
            }
        }
    }
}
//Standard Preview
struct LendingDataView_Previews: PreviewProvider {
    //Use the preview container
    static let context = PersistenceController.preview.container.viewContext
    static var sampleItem = Item(context: context)
    static var previews: some View {
        LendingDataView(item: sampleItem)
    }
}

extension Optional where Wrapped == LendingData {
    var _bound: LendingData? {
        get {
            return self
        }
        set {
            self = newValue
        }
    }
    var bound: LendingData {
        get {
            return _bound ?? LendingData.blank()
        }
        set {
            _bound = newValue
        }
    }
}

就像我一开始说的，class 是最安全的方法，但您可以使用 struct.

Like I said at the start class is the safest way but you can use the struct.

选项 2

只需添加一个名为 lendingDataJSON 的 attribute 类型 String? INSTEAD 的 lendingData 类型的 >可转换

Just add an an attribute named lendingDataJSON of Type String? INSTEAD of the lendingData of type Transformable

struct LendingData : Codable, Identifiable{
    let id: String
    var userName : String
    var amount : String
    var date : String
    var type : String
    var witnessDetails : [WitnessData]
    
    static func sample() -> LendingData {
        LendingData(id: UUID().uuidString, userName: "sample name", amount: "10.00", date: "(Date())", type: "sample type", witnessDetails: [WitnessData.sample(), WitnessData.sample()])
    }
    static func blank() -> LendingData {
        LendingData(id: UUID().uuidString, userName: "", amount: "", date: "", type: "", witnessDetails: [])
    }
}
struct WitnessData: Codable, Identifiable{
    let id: String
    var name: String
    static func sample() -> WitnessData{
        WitnessData( id: UUID().uuidString, name: UUID().uuidString)
    }
    static func blank() -> WitnessData{
        WitnessData( id: UUID().uuidString, name: "")
    }
}
//The App's CoreData Model will need an attibute
// named lendingDataJSON of Type String
extension Item{
    //This computed property should be the only way that the app alters the LendingData
    //If you use the lendingDataJSON directly you can corrupt all of it
    var lendingData: LendingData?{
        get{
            let decoder = JSONDecoder()
            if let obj = try? decoder.decode(LendingData.self, from: self.lendingDataJSON?.data(using: .utf8) ?? Data()) {
                return obj
            }else{
                return nil
            }
        }
        set{
            let encoder = JSONEncoder()
            encoder.outputFormatting = .prettyPrinted
            if let encoded = try? encoder.encode(newValue) {
                self.lendingDataJSON = String(data: encoded, encoding: .utf8) ?? ""
            }
        }
    }
}

所有 View 代码将与 class 选项或 struct 选项一起工作

All the View code will work the same with the class option or with the struct option

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