SwiftUI Firebase。删除所有项目而不仅仅是一个答案

【问题标题】：SwiftUI Firebase. Deletes all Items not just oneSwiftUI Firebase。删除所有项目而不仅仅是一个
【发布时间】：2020-05-02 18:36:53
【问题描述】：

我想删除带有其 ID (let db = Firestore.firestore()db.collection("Warenkorb").document(i.id).delete()) 的项目。所以这是我的代码。可悲的是，当我删除一个项目时，集合中的所有项目也会被删除。为什么？有人可以帮我吗？

ForEach(cart.data) { i in
     HStack{
         Image("pic").resizable().scaledToFit().frame(width: 50, height: 75, alignment: .leading).padding().foregroundColor(.black)
            Spacer()
            VStack(alignment: .leading){
                Text(i.name).font(.system(size: 25)).foregroundColor(.black)
                HStack{
                Text(i.preis).font(.system(size: 20)).foregroundColor(.black)
              Text(i.size).font(.system(size: 20)).foregroundColor(.black)
                }
         }
       Spacer()
        Text("\(i.quantity)").font(.system(size: 25)).foregroundColor(.black)
       Spacer()
                       if self.remove{

        Button(action: {
        let db = Firestore.firestore()
            db.collection("Warenkorb").document(i.id).delete()
            self.show.toggle()
            self.show.toggle()


                                    }) {
                        Image(systemName: "minus.circle.fill")
                                .resizable()
                        .frame(width: 20, height: 20)
                    .foregroundColor(.red)

            }
                        }
        Spacer()

     }
     .background(Color("Color-1")).frame(width: 350, height:  100).cornerRadius(30).padding(.leading)

}

【问题讨论】：

标签： firebase google-cloud-firestore swiftui

【解决方案1】：

您不应在 SwiftUI 视图中添加数据访问代码。相反，实现一个视图模型（以及可选的存储库）来管理您的数据。

我已经稍微修改了你的代码：

查看

struct ShoppingCartView: View {
  @ObservedObject var viewModel: ShoppingCartViewModel

  var body: some View {
    List {
      ForEach(viewModel.lineItems) { lineItem in
        VStack(alignment: .leading) {
          Text(lineItem.title)
            .font(.headline)
        }
      }
      .onDelete { indexSet in
        self.viewModel.deleteLineItems(at: indexSet)
      }
    }
  }

}

查看模型

import Foundation
import FirebaseFirestore
import FirebaseFirestoreSwift
import Combine

class ShoppingCartViewModel: ObservableObject {
  @Published var lineItems = [LineItem]()

  private var db = Firestore.firestore()
  private var listenerRegistration: ListenerRegistration?

  private var cancellables = Set<AnyCancellable>()

  init() {
    fetchData()
  }

  deinit {
    unregister()
  }

  func unregister() {
    if listenerRegistration != nil {
      listenerRegistration?.remove()
    }
  }

  func fetchData() {
    unregister()

    listenerRegistration = db.collection("shoppingCart").addSnapshotListener { (querySnapshot, error) in
      guard let documents = querySnapshot?.documents else {
        print("No documents")
        return
      }

      self.lineItems = documents.compactMap { queryDocumentSnapshot -> LineItem? in
        let lineItem = try? queryDocumentSnapshot.data(as: LineItem.self)
        return lineItem
      }
    }
  }

  func deleteLineItems(at offsets: IndexSet) {
    let itemsToDelete = offsets.lazy.map { self.lineItems[$0] }
    itemsToDelete.forEach { lineItem in
      if let id = lineItem.id {
        db.collection("shoppingCart").document(id).delete()
      }
    }
  }
}

【讨论】：