Created
April 27, 2019 18:41
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Extensions giving Swift's decodable API type inference super powers
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| // Private supporting types | |
| private struct AnyCodingKey: CodingKey { | |
| var stringValue: String | |
| var intValue: Int? | |
| init(_ string: String) { | |
| stringValue = string | |
| } | |
| init?(stringValue: String) { | |
| self.stringValue = stringValue | |
| } | |
| init?(intValue: Int) { | |
| self.intValue = intValue | |
| self.stringValue = String(intValue) | |
| } | |
| } | |
| // Safe Decoding Container | |
| public struct SafeDecodingContainer<Base: Decodable>: Decodable { | |
| public let value: Base? | |
| public init(from decoder: Decoder) throws { | |
| do { | |
| let container = try decoder.singleValueContainer() | |
| self.value = try container.decode(Base.self) | |
| } catch { | |
| print("Mapping ERROR: \(error)") | |
| self.value = nil | |
| } | |
| } | |
| } | |
| //Helpers | |
| public extension Decoder { | |
| func decode<T: Decodable>(_ key: String, as type: T.Type = T.self) throws -> T { | |
| return try decode(AnyCodingKey(key), as: type) | |
| } | |
| func decode<T: Decodable, K: CodingKey>(_ key: K, as type: T.Type = T.self) throws -> T { | |
| let container = try self.container(keyedBy: K.self) | |
| return try container.decode(type, forKey: key) | |
| } | |
| func decodeGuard<T: Decodable>(_ key: String) throws -> T? { | |
| return try? self.decodeGuard(T.self, forKey: AnyCodingKey(key)) | |
| } | |
| func decodeGuard<T: Decodable, K: CodingKey>(_ type: T.Type, forKey key: K) throws -> T? { | |
| let container = try? self.container(keyedBy: K.self) | |
| return tryOrNil { (try container?.decode(T.self, forKey: key)) } | |
| } | |
| func decodeGuardArray<T: Decodable>(_ key: String) throws -> [T] { | |
| return try decodeGuardArray(T.self, forKey: AnyCodingKey(key)) | |
| } | |
| func decodeGuardArray<T: Decodable, K: CodingKey>(_ type: T.Type, forKey key: K) throws -> [T] { | |
| let container = try? self.container(keyedBy: K.self) | |
| let array = tryOrNil { (try container?.decode([T].self, forKey: key)) } | |
| return array?.compactMap { $0 } ?? [] | |
| } | |
| } | |
| // example code | |
| public struct SaveDecodeClass: Codable { | |
| public var token: String = "" | |
| public var urlString: String = "" | |
| public init(from decoder: Decoder) throws { | |
| token = try decoder.decodeGuard("token") ?? "" | |
| urlString = try decoder.decodeGuard("urlString") ?? "" | |
| } | |
| } |
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