Swift 4 Decodable - No value associated with key CodingKeys [duplicate] - json

Question

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How do I use custom keys with Swift 4's Decodable protocol?
(4 answers)
Closed 3 years ago.
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
}