过滤大型 Array Swift

问题描述

我正在构建一个旅行计划应用，让用户可以使用 Picker 从本地 json 文件中选择一个城市。

json 文件有 115K 项，如果我尝试过滤这么多项，UI 会冻结。关于如何提高效率的任何建议。

任何帮助将不胜感激。

import SwiftUI

struct AddTripView: View {

    let cities = Bundle.main.decode([Destination].self,from: "cities.json")
    @State private var selectedCity = 0
    @State var searchText = ""

       var body: some View {
        
            Form {
                Section {
                    Picker(selection: $selectedCity,label: Text("Select city")) {
                        
                        SearchBar(text: $searchText)
 
                        ForEach(cities.filter {searchText.isEmpty ? true : $0.city.lowercased().hasPrefix(searchText.lowercased())},id: \.self) {
                            
                            Text($0.city)
                        }
                    }
                }
            }.navigationBarTitle("Create trip")
            
        }
}

struct AddTripView_Previews: PreviewProvider {
    static var previews: some View {
        AddTripView()
    }
}

JSON 示例

[{
    "id": 1,"city": "Zaranj","country": "Afghanistan"
  },{
    "id": 2,"city": "Taloqan",{
    "id": 3,"city": "Shīnḏanḏ",{
    "id": 4,"city": "Shibirghān",{
    "id": 5,"city": "Shahrak","country": "Afghanistan"
  }]

解决方法

你真的需要一个 Picker 吗？如果没有，你可以试试这个例子。 如果用户界面仍然存在问题，请告诉我们。

struct AddTripView: View {
    @State private var cities = [Destination]()
    @State private var selectedCity: Destination?
    @State private var searchQuery: String = ""
    
    var body: some View {
        VStack {
            Text("\(cities.count)")
            HStack {
                TextField("city search",text: $searchQuery).padding(5)
                    .overlay(RoundedRectangle(cornerRadius: 15).stroke(Color.blue,lineWidth: 1))
                    .foregroundColor(.blue)
                    .frame(width: 160)
                Button(action: {searchQuery = ""}) {
                    Image(systemName: "xmark.circle").font(.title)
                }
            }.padding(20)
            Divider()
            Text("Select city")

        ScrollView {
            LazyVStack (alignment: .leading) {
                ForEach(cities.filter{self.searchFor($0.city)}.sorted(by: { $0.city < $1.city })) { city in
                    Text("\(city.city)  \(city.country)")
                        .onTapGesture {
                            selectedCity = city
                            print("---> selectedCity: \(selectedCity?.city)")
                        }
                }
            }
        }.onAppear() {
                 cities = Bundle.main.decode([Destination].self,from: "cities.json")
            }
        }
    }
    
    private func searchFor(_ txt: String) -> Bool {
        return (txt.lowercased(with: .current).hasPrefix(searchQuery.lowercased(with: .current)) || searchQuery.isEmpty)
    }
}

struct Destination: Codable,Identifiable,Equatable {
    var id: Int
    var city: String
    var country: String
}