如何从firebase填充加载的记录？答案

【问题标题】：How to populate loaded records from firebase?如何从firebase填充加载的记录？
【发布时间】：2020-12-07 10:23:32
【问题描述】：

我编写了从 firebase 加载记录的函数，但出现错误

转义闭包捕获变异的“自我”参数

函数写法如下：

let db = Firestore.firestore()
@State var libraryImages: [LibraryImage] = []

mutating func loadImages() {
        libraryImages = []
        
        db.collection(K.FStore.CollectionImages.collectionName).getDocuments() { (querySnapshot, err) in
            if let err = err {
                print("Error getting documents: \(err)")
            } else {
                if let snapshotDocuments = querySnapshot?.documents {
                    for document in snapshotDocuments {
                        let documentData = document.data()
                        let title: String = documentData[K.FStore.CollectionImages.title] as! String
                        let thumbnailUrl: String = documentData[K.FStore.CollectionImages.thumbnailUrl] as! String
                        let svgUrl: String = documentData[K.FStore.CollectionImages.svgUrl] as! String
                        let libraryImageItem = LibraryImage(title: title, thumbnailUrl: thumbnailUrl, svgUrl: svgUrl)
                        self.libraryImages.append(libraryImageItem)
                    }
                }
            }
        }
    }

有谁知道导致错误的原因以及如何消除它？

【问题讨论】：

标签： swift firebase google-cloud-firestore swiftui

【解决方案1】：

将所有这些移动到引用类型视图模型中，并将其用作视图中的观察对象

这是一个可能的方法的演示：

struct DemoView: View {
  @ObservedObject var vm = ImagesViewModel()
//  @StateObject var vm = ImagesViewModel()       // << SwiftUI 2.0

  var body: some View {
     Text("Loaded images: \(vm.libraryImages.count)")
       .onAppear {
           self.vm.loadImages()
       }
  }
}


class ImagesViewModel: ObservableObject {
    let db = Firestore.firestore()
    @Published var libraryImages: [LibraryImage] = []

    func loadImages() {
        libraryImages = []

        db.collection(K.FStore.CollectionImages.collectionName).getDocuments() { (querySnapshot, err) in
            if let err = err {
                print("Error getting documents: \(err)")
            } else {
                if let snapshotDocuments = querySnapshot?.documents {
                    var images = [LibraryImage]()
                    for document in snapshotDocuments {
                        let documentData = document.data()
                        let title: String = documentData[K.FStore.CollectionImages.title] as! String
                        let thumbnailUrl: String = documentData[K.FStore.CollectionImages.thumbnailUrl] as! String
                        let svgUrl: String = documentData[K.FStore.CollectionImages.svgUrl] as! String
                        let libraryImageItem = LibraryImage(title: title, thumbnailUrl: thumbnailUrl, svgUrl: svgUrl)
                        images.append(libraryImageItem)
                    }

                    DispatchQueue.main.async {
                        self.libraryImages = images
                    }
                }
            }
        }
    }
}

【讨论】：