JSONEncoder().encode is always empty

Question

I have a class that it has the next

import UIKit

final class PruebaModel: Codable {
    
    let a: String?
    let b: String?
    let c: [D]?
    let f: String?
    
    
    enum CodingKeys: String, CodingKey {
        case a = "a"
        case b = "b"
        case c = "c"
        case f = "f"
    }
    
    required init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        a = try values.decodeIfPresent(String.self, forKey: .a)
        b = try values.decodeIfPresent(String.self, forKey: .b)
        c = try values.decodeIfPresent([D].self, forKey: .c)
        f = try values.decodeIfPresent(String.self, forKey: .f)
    }
    
    required init()  {
        a = ""
        b = ""
        c = Array<D>()
        f = ""
    }
}


import Foundation

struct D: Codable {
    let l: String
    let m: String
    
    enum CodingKeys: String, CodingKey {
        case l = "l"
        case m = "m"
    }
    
    init(from decoder: Decoder) throws {
        let value = try decoder.container(keyedBy: CodingKeys.self)
        l = try value.decode(String.self, forKey: .l)
        m = try value.decode(String.self, forKey: .m)
    }
    
    public func encode(to encoder: Encoder) throws {
        //Implement when needed
    }
}

The json is the next

{
     
     "a": "a",
     "b": "b",
     "c": [
       {
         "l": "¿Cuál es el mi color favorito?",
         "m":"QAUY.15"
       }
    ],
    "f": "f"
     
}

The class is perfect, it has the object with parameters, but when i try to convert the class for json. The array is empty

Code

let jsonData = try! JSONEncoder().encode(PruebaModel)
let jsonString = String(data: jsonData, encoding: .utf8)!

Result when i evaluated the expression

po String(data: try! JSONEncoder().encode(PruebaModel), encoding: .utf8)!

"{"a":"a","b":"b","c":[{}],"f":"f"}"

Why c is empty?. it has an object inside the array.

If The object is inside the array doesn't have special character, the decode shows the object

I deleted the previous comment since you updated the question... What's the actual object you're trying to encode? Is `D.encode(to:)` actually empty? — New Dev, Oct 20 '20 at 21:57
`PruebaModel` is a type - not an instance. Are you encoding (from an object to JSON) or decoding (from JSON to an object)? — New Dev, Oct 20 '20 at 21:59
Object-to-JSON is called "encoding". If you had an object `let pruebalModel = PruebalModel(....)`, then you could encode it with `JSONEncoder().encode(pruebalModel)`, but since `D.encode(to:)` is empty, it encodes into an empty JSON. Your code `JSONEncoder().encode(PruebalModel)` shouldn't even compile — New Dev, Oct 20 '20 at 22:02

matt · Answer 1 · 2020-10-21T00:57:04.630

1

Unclear what you're asking. For one thing, you've got way too much code. For another, the code you've shown makes no sense. The JSON you've shown, on the other hand, is perfectly well decodable into a PruebaModel, and a correctly constructed PruebaModel is encodable into your JSON:

struct D: Codable {
    let l: String
    let m: String
}
struct PruebaModel: Codable {
    let a: String?
    let b: String?
    let c: [D]?
    let f: String?
}
let jsonString = """
{
    "a": "a",
    "b": "b",
    "c": [
        {
            "l": "¿Cuál es el mi color favorito?",
            "m":"QAUY.15"
        }
    ],
    "f": "f"
    }
"""
let jsonData = jsonString.data(using: .utf8)!
let result = try? JSONDecoder().decode(PruebaModel.self, from: jsonData)
print(result?.c?.first?.l) // Optional("¿Cuál es el mi color favorito?")
// let's also try encoding
let d = D(l: "¿Cuál es el mi color favorito?", m: "QAUY.15")
let myPruebaModel = PruebaModel(a: "a", b: "b", c: [d], f: "f")
let jsonData2 = try? JSONEncoder().encode(myPruebaModel)
print(String(data: jsonData2!, encoding: .utf8)!)
// {"b":"b","c":[{"l":"¿Cuál es el mi color favorito?","m":"QAUY.15"}],"a":"a","f":"f"}

edited Oct 21 '20 at 00:57

answered Oct 20 '20 at 23:16

matt

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But i want to encode the object, the decode is functioned , but when i encode the object, it is not functioned – Alejandro Gonzalez Oct 20 '20 at 23:39
Yes, encoding works too. I've added code that proves it. Just copy and paste my code right into a playground and run it and see for yourself. – matt Oct 21 '20 at 00:56
i am going to check it, because i am debbuging and it is not functioned, the array is empty – Alejandro Gonzalez Oct 21 '20 at 14:15
Go ahead and check it, whatever that means The code I gave is a self contained example and works as shown. That’s just a fact. – matt Oct 21 '20 at 14:21

JSONEncoder().encode is always empty

1 Answers1