EmptyDecoded.swift

import Foundation

public protocol EmptyInitializable {
    init()
}
extension Int: EmptyInitializable {}
extension String: EmptyInitializable {}
extension Array: EmptyInitializable {}
extension Bool: EmptyInitializable {}

@propertyWrapper
public struct EmptyDecoded<T: Decodable & EmptyInitializable>: Decodable {
   public var wrappedValue: T

    public init(wrappedValue: T) {
        self.wrappedValue = wrappedValue
    }

    public init(from decoder: Decoder) throws {
        guard let container = try? decoder.singleValueContainer(),
            let value = try? container.decode(T.self) else {
                wrappedValue = T()
                return
        }
        wrappedValue = value
    }
}
extension EmptyDecoded: Equatable where T: Equatable {}
extension EmptyDecoded: Hashable where T: Hashable {}

extension KeyedDecodingContainer {
    public func decode<T>(_ type: EmptyDecoded<T>.Type, forKey key: K) throws -> EmptyDecoded<T> where T: Decodable & EmptyInitializable {
        try EmptyDecoded<T>(from: superDecoder(forKey: key))
    }
}

struct Spot: Decodable {
    var id: Int
    var name: String
    @EmptyDecoded
    var isGoodPlace: Bool
}

let string = #"{ "id": 300, "name": "AppBrew"}"#
print(try! JSONDecoder().decode(Spot.self, from: string.data(using: .utf8)!))