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Decoding JSON array **not** containing the same objects (Swift + Decodable)
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| let jsonString = """ | |
| { | |
| "items": [ | |
| { | |
| "id": 20, | |
| "type": "juice", | |
| "fruit": "orange" | |
| }, | |
| { | |
| "id": 99, | |
| "type": "soup", | |
| "vegetables": ["carrot", "potatoes", "turnip"] | |
| }, | |
| { | |
| "id": 12, | |
| "type": "milkshake", | |
| "composition": { | |
| "milk": "cow", | |
| "fruit": "kiwi" | |
| } | |
| } | |
| ] | |
| } | |
| """ | |
| guard let jsonData = jsonString.data(using: .utf8) else { fatalError("Input JSON could not be converted into Data.") } | |
| let jsonDecoded = try JSONDecoder().decode(JSON.self, from: jsonData) | |
| jsonDecoded.items.forEach { (item) in | |
| switch item { | |
| case is Soup: print("🥣 | \(item)") | |
| case is Milkshake: print("🥤 | \(item)") | |
| case is Juice: print("🍹 | \(item)") | |
| default: print("❓ | \(item)") | |
| } | |
| } | |
| //----------------------------// | |
| // PLAYGROUND OUTPUT CONSOLE // | |
| //----------------------------// | |
| // | |
| //🍹 | Item n°20 of type juice. Extra: orange | |
| //🥣 | Item n°99 of type soup. Extra: ["carrot", "potatoes", "turnip"] | |
| //🥤 | Item n°12 of type milkshake. Extra: Composition(milk: "cow", fruit: "kiwi") | |
| // | |
| //------------------------------ |
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| /// Allows to decode a JSON with unknown types. | |
| /// Inspiration: https://medium.com/grand-parade/parsing-fields-in-codable-structs-that-can-be-of-any-json-type-e0283d5edb | |
| public enum JSONValue: Decodable { | |
| case string(String) | |
| case int(Int) | |
| case double(Double) | |
| case bool(Bool) | |
| case object([String: JSONValue]) | |
| case array([JSONValue]) | |
| case nil | |
| var value: Any? { | |
| switch self { | |
| case .string(let value): return value | |
| case .int(let value): return value | |
| case .double(let value): return value | |
| case .bool(let value): return value | |
| case .object(let value): return value.mapValues { $0.value } | |
| case .array(let value): return value.map { $0.value } | |
| case .nil: return nil | |
| } | |
| } | |
| public init(from decoder: Decoder) throws { | |
| let container = try decoder.singleValueContainer() | |
| if let value = try? container.decode(String.self) { | |
| self = .string(value) | |
| } else if let value = try? container.decode(Int.self) { | |
| self = .int(value) | |
| } else if let value = try? container.decode(Double.self) { | |
| self = .double(value) | |
| } else if let value = try? container.decode(Bool.self) { | |
| self = .bool(value) | |
| } else if let value = try? container.decode([String: JSONValue].self) { | |
| self = .object(value) | |
| } else if let value = try? container.decode([JSONValue].self) { | |
| self = .array(value) | |
| } else if container.decodeNil() { | |
| self = .nil | |
| } else { | |
| throw DecodingError.typeMismatch(JSONValue.self, DecodingError.Context(codingPath: container.codingPath, debugDescription: "Not a JSON.")) | |
| } | |
| } | |
| func data() throws -> Data? { | |
| guard let value = value else { return nil } | |
| return try JSONSerialization.data(withJSONObject: value, options: []) | |
| } | |
| } |
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| class Juice: Item { | |
| let fruit: String | |
| private enum CodingKeys: String, CodingKey { | |
| case fruit | |
| } | |
| required init(from decoder: Decoder) throws { | |
| let container = try decoder.container(keyedBy: CodingKeys.self) | |
| fruit = try container.decode(String.self, forKey: .fruit) | |
| try super.init(from: decoder) | |
| } | |
| override var debugDescription: String { | |
| return "\(super.debugDescription). Extra: \(fruit)" | |
| } | |
| } | |
| class Soup: Item { | |
| let vegetables: [String] | |
| private enum CodingKeys: String, CodingKey { | |
| case vegetables | |
| } | |
| required init(from decoder: Decoder) throws { | |
| let container = try decoder.container(keyedBy: CodingKeys.self) | |
| vegetables = try container.decode([String].self, forKey: .vegetables) | |
| try super.init(from: decoder) | |
| } | |
| override var debugDescription: String { | |
| return "\(super.debugDescription). Extra: \(vegetables)" | |
| } | |
| } | |
| class Milkshake: Item { | |
| let composition: Composition | |
| private enum CodingKeys: String, CodingKey { | |
| case composition | |
| } | |
| required init(from decoder: Decoder) throws { | |
| let container = try decoder.container(keyedBy: CodingKeys.self) | |
| composition = try container.decode(Milkshake.Composition.self, forKey: .composition) | |
| try super.init(from: decoder) | |
| } | |
| override var debugDescription: String { | |
| return "\(super.debugDescription). Extra: \(composition)" | |
| } | |
| } | |
| extension Milkshake { | |
| struct Composition: Decodable { | |
| let milk: String | |
| let fruit: String | |
| } | |
| } | |
| class Item: Decodable, CustomDebugStringConvertible { | |
| let id: Int | |
| let type: String | |
| private enum CodingKeys: String, CodingKey { | |
| case id | |
| case type | |
| } | |
| required init(from decoder: Decoder) throws { | |
| let container = try decoder.container(keyedBy: CodingKeys.self) | |
| id = try container.decode(Int.self, forKey: .id) | |
| type = try container.decode(String.self, forKey: .type) | |
| } | |
| var debugDescription: String { | |
| return "Item n°\(id) of type \(type)" | |
| } | |
| } | |
| class JSON: Decodable { | |
| let items: [Item] | |
| private enum CodingKeys: String, CodingKey { | |
| case items | |
| } | |
| required init(from decoder: Decoder) throws { | |
| let container = try decoder.container(keyedBy: CodingKeys.self) | |
| let values = try container.decode([JSONValue].self, forKey: .items) | |
| items = try values.map { value -> Item in | |
| guard let data = try value.data() | |
| else { throw DecodingError.dataCorruptedError(forKey: .items, in: container, debugDescription: "Cannot convert \(value) into Data.") } | |
| if let juice = try? JSONDecoder().decode(Juice.self, from: data) { | |
| return juice | |
| } else if let soup = try? JSONDecoder().decode(Soup.self, from: data) { | |
| return soup | |
| } else if let milkshake = try? JSONDecoder().decode(Milkshake.self, from: data) { | |
| return milkshake | |
| } else { | |
| throw DecodingError.dataCorruptedError(forKey: .items, in: container, debugDescription: "Unknown decoder for data: \(String(data: data, encoding: .utf8) ?? "?_?").") | |
| } | |
| } | |
| } | |
| } |
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