無法創建變數

我在創建變數時遇到問題。這是我想做的一個例子：

我在 [ ] 中有 JSON 資料。我在選擇器中選擇 smth，這會改變pickerSelection1，我可以在視圖中顯示這個字串。代碼如下所示：

var cc1: String {
        guard api.currencyCode1.count > 0 else {
            return "err"
        }
        let cc1 = api.currencyCode1[pickerSelection1]
        return cc1
    }
    

這是我在新專案中嘗試做的事情：

  var cc1: String {
        guard api.currencies.count > 0 else {
            return "err"
        }
        ForEach(api.currencies, id: \.self) { cc1 in // BUG: Static method 'buildBlock' requires that 'String.SubSequence' (aka 'Substring') conform to 'AccessibilityRotorContent'
            let cc1 = cc1.currencyCode[$pickerSelection1] // BUG: Subscript 'subscript(_:)' requires that 'Binding<Int>' conform to 'RangeExpression'
            cc1
        }
    }

我很確定我做錯了，我不應該使用: String { }. 需要你的建議，女士們，先生們。

PS：這是整個代碼：

// Model
import Foundation

struct CurrencyModel: Codable {
    var results: [String:Double]
}

struct CurrencyNewModel: Codable {
    var currencies: [String:String]
}

struct Currency: Codable, Hashable {
    let currencyCode: String
    let fullName: String
    var price: Double
}

// ViewModel
import SwiftUI


class CurrencyViewModel: ObservableObject {
    
    @Published var currencies: [Currency] = []

          init() {
              fetchNewData { [self] (currency) in
                  switch currency {
                  case .success(let names):
                      print("Success")
                      DispatchQueue.main.async {
                          self.currencies = names.currencies.map {
                          Currency(currencyCode: $0.key, fullName: $0.value, price: 0)
                          }
                      }
                      fetchData { result in
                          switch result {
                          case .success(let prices):
                              print("Success")
                              
                   
                              for (index, value) in currencies.enumerated() {
                                  if let price = prices.results.first(where: { $0.key == value.currencyCode }) {
                                      DispatchQueue.main.async {
                                      currencies[index].price = price.value
                                        }
                                      }
                                  }
                          case .failure(let error):
                              print(error)
                          }
                      }
                  case .failure(let error):
                      print("Error", error)
        }
    }
}
      
     
    
   
    
func fetchData(completion: @escaping (Result<CurrencyModel,Error>) -> ()) {
    guard let url = URL(string: "https://api.fastforex.io/fetch-all?from=USD&api_key=7ffe65c2ef-926f01d9e8-r7eql2") else { return }
    URLSession.shared.dataTask(with: url) { data, responce, error in
        if let error = error {
            completion(.failure(error))
            return
        }
        
        guard let safeData = data else { return }
        
        do {
            let currency = try JSONDecoder().decode(CurrencyModel.self, from: safeData)
            completion(.success(currency))
        }
        catch {
            completion(.failure(error))
        }
    }
    .resume()
    
    
    }
    func fetchNewData(completion: @escaping (Result<CurrencyNewModel,Error>) -> ()) {
        guard let url = URL(string: "https://api.fastforex.io/currencies?api_key=7ffe65c2ef-926f01d9e8-r7eql2") else { return }
        URLSession.shared.dataTask(with: url) { data, responce, error in
            if let error = error {
                completion(.failure(error))
                return
            }
            
            guard let safeData = data else { return }
            
            do {
                let currency = try JSONDecoder().decode(CurrencyNewModel.self, from: safeData)
                completion(.success(currency))
            }
            catch {
                completion(.failure(error))
            }
        }
        .resume()
        
    }

} 

// View
import SwiftUI

struct CurrencyView: View {
    
    @StateObject var api = CurrencyViewModel()
    
    @State var pickerSelection1 = 1
    @State var pickerSelection2 = 1
    
    var body: some View {
        
        VStack {
            Picker("", selection: $pickerSelection1) {
            ForEach(api.currencies, id: \.self) { c1 in
                Text(c1.currencyCode   " "   c1.fullName)
                }
            }
            .id(UUID())
            .labelsHidden()
            
            Picker("", selection: $pickerSelection2) {
            ForEach(api.currencies, id: \.self) { c2 in
                Text(c2.currencyCode   " "   c2.fullName)
                }
            }
            .id(UUID())
            .labelsHidden()
            
            
        }
    }
    
    var cc1: String {
        guard api.currencies.count > 0 else {
            return "err"
        }
        ForEach(api.currencies, id: \.self) { cc1 in
            let cc1 = cc1.currencyCode[$pickerSelection1]
            cc1
        }
    }
}
    
struct CurrencyView_Previews: PreviewProvider {
    static var previews: some View {
        CurrencyView()
    }
}

uj5u.com熱心網友回復：

ForEach僅用于回傳Views

你應該使用

for cc1 in api.currencies{
    //The rest of your code
}

并且pickerSelection1不使用$

另一個問題可能是型別與 的pickerSelection1型別不匹配c1。

它們應該匹配，否則操作的選擇部分將無法按您的預期作業。

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