NIL 值解码嵌套 JSON - SwiftUI答案

【问题标题】：NIL value decoding nested JSON - SwiftUINIL 值解码嵌套 JSON - SwiftUI
【发布时间】：2020-05-09 13:54:29
【问题描述】：

我在解码“相当简单”的嵌套 JSON 时收到 nil，我在这里缺少什么？

NetworkController 部分（连同整个 ContentView）与“普通”JSON（即 {"greetings": "hi"}）完美配合，但我仍然得到带有嵌套 JSON 结构的 nil

这是我的 JSON：

index.json

{
  "products": {
    "pasta": 81.22,
    "pizza": 13.81,
    "apples": 0,
    "sausages": 2.36,
    "potatoes": 0.55,
    "cucmbers": 2.06,
    "oranges": 0
  }
}

这是我的代码：

DataStruct.swift

struct ProductWrapper: Decodable {
    var products: Product
}

struct Product: Decodable {
    var pasta: Double
    var pizza: Double
    var apples: Double
    var sausages: Double
    var potatoes: Double
    var cucmbers: Double
    var oranges: Double
}

ContentView.swift

import SwiftUI

class ProductsList: ObservableObject {
    @Published var prods: ProductWrapper? = nil
    func fetchProducts() {
        NetworkController.fetchProducts { prods in
            self.prods = prods
        }
    }
}

struct ContentView: View {

    @ObservedObject var DecodedProducts = ProductsList()

    var body: some View {

        VStack{

            HStack{
                Text("Pasta: ")
                Text(String("\(self.DecodedProducts.prods?.products.pasta)")).fontWeight(.bold).foregroundColor(.red)
            }

            HStack{
                Text("Pizza: ")
                Text(String("\(self.DecodedProducts.prods?.products.pizza)")).fontWeight(.bold).foregroundColor(.blue)
            }

            HStack{
                Text("Apples: ")
                Text(String("\(self.DecodedProducts.prods?.products.apples)")).fontWeight(.bold).foregroundColor(.green)
            }

        }.padding()
    }
}

NetworkManager.swift

import Foundation

struct NetworkController {
    static func fetchProducts(completion: @escaping ((ProductWrapper) -> Void)) {
        if let url = URL(string: "http://localhost:1234/index.json") {
            let request = URLRequest(url: url)
            URLSession.shared.dataTask(with: request) { (data, resp, err) in
                do {
                    if let products = data {
                        let prods = try JSONDecoder().decode(ProductWrapper.self, from: products)
                        DispatchQueue.main.async() {
                            completion(prods)
                        }
                    } else {
                        print("Error Found")
                    }
                } catch let err as NSError {
                    print(err.localizedDescription)
                }
            }.resume()
        }
    }
}

提前致谢！

【问题讨论】：

标签： json swiftui

【解决方案1】：

发现问题；

那只是一个愚蠢的我......

忘记在onAppear中调用fetchProducts() *facepalm*

.onAppear{
self.DecodedProducts.fetchProducts()
}

这是正确的代码：

ContentView.swift

import SwiftUI

class ProductsList: ObservableObject {
    @Published var prods: ProductWrapper? = nil
    func fetchProducts() {
        NetworkController.fetchProducts { prods in
            self.prods = prods
        }
    }
}

struct ContentView: View {

    @ObservedObject var DecodedProducts = ProductsList()



    var body: some View {

        VStack{

            HStack{
                Text("Pasta: ")
                Text(String("\(self.DecodedProducts.prods?.products.pasta ?? 0)")).fontWeight(.bold).foregroundColor(.red)
            }

            HStack{
                Text("Pizza: ")
                Text(String("\(self.DecodedProducts.prods?.products.pizza ?? 0)")).fontWeight(.bold).foregroundColor(.blue)
            }

            HStack{
                Text("Apples: ")
                Text(String("\(self.DecodedProducts.prods?.products.apples ?? 0)")).fontWeight(.bold).foregroundColor(.green)
            }

        }.onAppear{
            self.DecodedProducts.fetchProducts()
            }
        }
    }

【讨论】：