我正在嘗試設定 SwiftUI 天氣應用程式。當用戶在文本欄位中搜索城市名稱然后點擊搜索按鈕時，導航鏈接串列項應出現在串列中。然后，用戶應該能夠單擊導航鏈接并重新定向到詳細資訊視圖。我的目標是讓搜索到的導航鏈接填充串列。但是，我的搜索城市沒有出現在串列中，我不知道為什么。在 ContentView 中，我設定了一個帶有 ForEach 函式的串列，該函式傳入 cityNameList，它是 WeatherViewModel 的一個實體。我的期望是 Text(city.title) 應該顯示為 NavigationLink 串列項。我應該如何配置 ContentView 或 ViewModel 以使用 NavigationLink 串列項填充串列？請參閱下面的我的代碼：
內容視圖
import SwiftUI
struct ContentView: View {
// Whenever something in the viewmodel changes, the content view will know to update the UI related elements
@StateObject var viewModel = WeatherViewModel()
@State private var cityName = ""
var body: some View {
NavigationView {
VStack {
TextField("Enter City Name", text: $cityName).textFieldStyle(.roundedBorder)
Button(action: {
viewModel.fetchWeather(for: cityName)
cityName = ""
}, label: {
Text("Search")
.padding(10)
.background(Color.green)
.foregroundColor(Color.white)
.cornerRadius(10)
})
List {
ForEach(viewModel.cityWeather, id: \.id) { city in
NavigationLink(destination: DetailView(detail: viewModel)) {
HStack {
Text(city.cityWeather.name)
.font(.system(size: 32))
}
}
}
}
Spacer()
}
.navigationTitle("Weather MVVM")
}.padding()
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
視圖模型
import Foundation
class WeatherViewModel: ObservableObject {
//everytime these properties are updated, any view holding onto an instance of this viewModel will go ahead and updated the respective UI
@Published var cityWeather: WeatherModel = WeatherModel()
func fetchWeather(for cityName: String) {
guard let url = URL(string: "https://api.openweathermap.org/data/2.5/weather?q=\(cityName)&units=imperial&appid=<MyAPIKey>") else {
return
}
let task = URLSession.shared.dataTask(with: url) { data, _, error in
// get data
guard let data = data, error == nil else {
return
}
//convert data to model
do {
let model = try JSONDecoder().decode(WeatherModel.self, from: data)
DispatchQueue.main.async {
self.cityWeather = model
}
}
catch {
print(error)
}
}
task.resume()
}
}
模型
import Foundation
struct WeatherModel: Identifiable, Codable {
var id = UUID()
var name: String = ""
var main: CurrentWeather = CurrentWeather()
var weather: [WeatherInfo] = []
func firstWeatherInfo() -> String {
return weather.count > 0 ? weather[0].description : ""
}
}
struct CurrentWeather: Codable {
var temp: Float = 0.0
}
struct WeatherInfo: Codable {
var description: String = ""
}
詳細視圖
import SwiftUI
struct DetailView: View {
var detail: WeatherViewModel
var body: some View {
VStack(spacing: 20) {
Text(detail.cityWeather.name)
.font(.system(size: 32))
Text("\(detail.cityWeather.main.temp)")
.font(.system(size: 44))
Text(detail.cityWeather.firstWeatherInfo())
.font(.system(size: 24))
}
}
}
struct DetailView_Previews: PreviewProvider {
static var previews: some View {
DetailView(detail: WeatherViewModel.init())
}
}
uj5u.com熱心網友回復：
試試這個示例代碼，對我來說效果很好：
struct WeatherModel: Identifiable, Codable {
let id = UUID()
var name: String = ""
var main: CurrentWeather = CurrentWeather()
var weather: [WeatherInfo] = []
func firstWeatherInfo() -> String {
return weather.count > 0 ? weather[0].description : ""
}
}
struct CurrentWeather: Codable {
var temp: Float = 0.0
}
struct WeatherInfo: Codable {
var description: String = ""
}
struct ContentView: View {
// Whenever something in the viewmodel changes, the content view will know to update the UI related elements
@StateObject var viewModel = WeatherViewModel()
@State private var cityName = ""
var body: some View {
NavigationView {
VStack {
TextField("Enter City Name", text: $cityName).textFieldStyle(.roundedBorder)
Button(action: {
viewModel.fetchWeather(for: cityName)
cityName = ""
}, label: {
Text("Search")
.padding(10)
.background(Color.green)
.foregroundColor(Color.white)
.cornerRadius(10)
})
List {
ForEach(viewModel.cityNameList) { city in
NavigationLink(destination: DetailView(detail: city)) {
HStack {
Text(city.name).font(.system(size: 32))
}
}
}
}
Spacer()
}.navigationTitle("Weather MVVM")
}.navigationViewStyle(.stack)
}
}
struct DetailView: View {
var detail: WeatherModel
var body: some View {
VStack(spacing: 20) {
Text(detail.name).font(.system(size: 32))
Text("\(detail.main.temp)").font(.system(size: 44))
Text(detail.firstWeatherInfo()).font(.system(size: 24))
}
}
}
class WeatherViewModel: ObservableObject {
@Published var cityNameList = [WeatherModel]()
func fetchWeather(for cityName: String) {
guard let url = URL(string: "https://api.openweathermap.org/data/2.5/weather?q=\(cityName)&units=imperial&appid=YOURKEY") else { return }
let task = URLSession.shared.dataTask(with: url) { data, _, error in
guard let data = data, error == nil else { return }
do {
let model = try JSONDecoder().decode(WeatherModel.self, from: data)
DispatchQueue.main.async {
self.cityNameList.append(model)
}
}
catch {
print(error) // <-- you HAVE TO deal with errors here
}
}
task.resume()
}
}
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