SwiftUI 中如何优化下面这种场景?

封装了几个网络请求:

class API: ObservableObject {
    @Published private(set) var isAccessTokenValid = false
    @AppStorage("Passcode") var passcode: String = ""
    @AppStorage("AccessToken") var accessToken: String = ""
    @AppStorage("RefreshToken") var refreshToken: String = ""
    privite func request() async throws -> (T?, URLResponse?) where T : Decodable {
       // 省略具体实现
    }
    func request1() async throws -> SomeResponseType {}
    func request2() async throws -> SomeResponseType {}
    func request3() async throws -> SomeResponseType {}
}

在 @main 中, 使用 .environmentObject(API()) 将网络请求加入到全局环境中, 在每个页面用到它的地方使用 @EnvironmentObject var api: API 来获取.

比如进入页面 A 需要进行网络请求, 则:

struct A: View {
  @EnvironmentObject var api: API
  @State private var data: [SomeResponseType] = []
  var body: View {
    VStack {}
    .task {
      let r = try? await api.request1()
      if let d = r {
        data = d
      }
    }
  }
}

但这样的代码是 UIKit 的思路, 在 SwiftUI 中应该使用 Model 层进行网络请求, 应该这样添加一层 Model:

class ModelA: ObservableObject {
  @Published var data: [SomeResponseType]
  init() {
    // do the request and then init data using the response
  }
}

在页面中只需要

struct A: View {
  @StateObject private var model = ModelA()
  var body: View {
    VStack {
      model.data...
    }
  }
}

但现在问题出现了, 在 Model 里面无法直接使用上面封装的 API, 也就是在 model 的初始化函数中, 无法获取 environment 数据. 于是只能修改一下 API, 使其变成单例:

class API: ObservableObject {
   static let shared = API()
   ...
}

这样在 model 里直接可以使用它了.

虽然这样看起来解决了, 但感觉代码结构还需要调整一下, 但不知道如何调整. 请大佬指点指点

MakHoCheung

2022-12-13 15:14:08 +08:00

我觉得你一开始的方式没问题，苹果官方例子都是这样子，没必要优化掉 task modifier
摘自 Food Truck
```
struct TruckWeatherCard: View {
var location: CLLocation
var headerUsesNavigationLink: Bool = false
var navigation: TruckCardHeaderNavigation = .navigationLink

@State private var forecast: TruckWeatherForecast = placeholderForecast

var body: some View {
VStack {
CardNavigationHeader(panel: .city(City.sanFrancisco.id), navigation: navigation) {
Label("Forecast", systemImage: "cloud.sun")
}

chart
.frame(minHeight: 180)
}
.padding(10)
.background()
.task {
do {
let weather = try await WeatherService.shared.weather(for: location, including: .hourly).forecast
forecast = TruckWeatherForecast(entries: weather.map {
.init(
date: $0.date,
degrees: $0.temperature.converted(to: .fahrenheit).value,
isDaylight: $0.isDaylight
)
})
} catch {
print("Could not load weather", error.localizedDescription)
}
}
}

................

}
```