Swift 4 Decodable - No value associated with key CodingKeys

Question

I'm decoding a JSON response in my Swift App, and the code used to work till it decided to stop working.

this is my json reposnse

{"foods":[{"food_name":"Milk Chocolate","brand_name":"Snickers","serving_weight_grams":41.7,"nf_calories":212.3,"nf_total_fat":11.6,"nf_saturated_fat":4,"nf_total_carbohydrate":22.7,"nf_protein":3.9}]}

And this is the code to decode my json

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
        guard let data = data else { return }

        print(String(data: data, encoding: .utf8)!)
        do {
            //Decode dataResponse received from a network request
            let decoder = JSONDecoder()
            let foods = try decoder.decode(JSONFoods.self, from: data) //Decode JSON Response Data

            self.jsonfood = foods.JSONFood[0]
            print(self.jsonfood!)

        } catch let parsingError {
            print("Error", parsingError)
        }

    }
    task.resume()

And my Structs are

struct JSONFoods: Decodable {
var JSONFood: [JSONFood]    
}

struct JSONFood: Decodable{
var food_name: String
var brand_name: String
var nf_calories: Int
var nf_protein: Int
var nf_total_fat: Int
var nf_total_carbohydrate: Int
var serving_weight_grams: Int
}

And the error message I get is this

keyNotFound(CodingKeys(stringValue: "JSONFood", intValue: nil), Swift.DecodingError.Context(codingPath: [], debugDescription: "No value associated with key CodingKeys(stringValue: \"JSONFood\", intValue: nil) (\"JSONFood\").", underlyingError: nil))

And if i get replace decode(JSONFoods.self, from: data) with decode(JSONFood.self, from: data) I get this error message

keyNotFound(CodingKeys(stringValue: "food_name", intValue: nil), Swift.DecodingError.Context(codingPath: [], debugDescription: "No value associated with key CodingKeys(stringValue: \"food_name\", intValue: nil) (\"food_name\").", underlyingError: nil))

I searched everywhere with no luck, any help is very appreciated

Answer 1

You need

struct Root: Codable {
    let foods: [Food]
}

struct Food: Codable {
    let foodName: String?
    let  brandName: String
    let servingWeightGrams, nfCalories, nfTotalFat: Double
    let nfSaturatedFat: Int
    let nfTotalCarbohydrate, nfProtein: Double

    enum CodingKeys: String, CodingKey {
        case foodName = "food_name"
        case brandName = "brand_name"
        case servingWeightGrams = "serving_weight_grams"
        case nfCalories = "nf_calories"
        case nfTotalFat = "nf_total_fat"
        case nfSaturatedFat = "nf_saturated_fat"
        case nfTotalCarbohydrate = "nf_total_carbohydrate"
        case nfProtein = "nf_protein"
    }
}

First : you make JSONFood while it should be foods

Second :food_name doesn't exist in current json root so this will fail

let foods = try decoder.decode(JSONFoods.self, from: data) //Decode JSON Response Data

---

In case to take advantage of convertFromSnakeCase

let str = """

{"foods":[{"food_name":"Milk Chocolate","brand_name":"Snickers","serving_weight_grams":41.7,"nf_calories":212.3,"nf_total_fat":11.6,"nf_saturated_fat":4,"nf_total_carbohydrate":22.7,"nf_protein":3.9}]}

"""

    do {
        let res = JSONDecoder()
        res.keyDecodingStrategy = .convertFromSnakeCase
        let ss = try res.decode(Root.self, from:Data(str.utf8))
        print(ss)
    }
    catch {
        print(error)
    }

---

struct Root: Codable {
    let foods: [Food]
}

struct Food: Codable {
    let foodName: String?
    let  brandName: String
    let servingWeightGrams, nfCalories, nfTotalFat: Double
    let nfSaturatedFat: Int
    let nfTotalCarbohydrate, nfProtein: Double
}