Created
January 1, 2021 19:05
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A Gist to decode SEREVR response if associated keys are not available in each fetch from server.
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| protocol DefaultSourceValue { | |
| associatedtype Value: Decodable | |
| static var defaultValue: Value {get} | |
| } | |
| enum DefaultValue {} //this will not allow for default init | |
| extension DefaultValue { | |
| @propertyWrapper | |
| struct WrappedValue<Source: DefaultSourceValue> { | |
| typealias Value = Source.Value | |
| var wrappedValue = Source.defaultValue | |
| } | |
| } | |
| extension DefaultValue.WrappedValue: Decodable { | |
| init(from decoder: Decoder) throws { | |
| let container = try decoder.singleValueContainer() | |
| self.wrappedValue = try container.decode(Value.self) | |
| } | |
| } | |
| extension KeyedDecodingContainer { | |
| func decode<T>(_ type: DefaultValue.WrappedValue<T>.Type, forKey key: Key) throws -> DefaultValue.WrappedValue<T> { | |
| try decodeIfPresent(type.self, forKey: key) ?? .init() | |
| } | |
| } | |
| extension DefaultValue { | |
| typealias Source = DefaultSourceValue | |
| typealias List = Decodable & ExpressibleByArrayLiteral | |
| typealias Map = Decodable & ExpressibleByDictionaryLiteral | |
| enum Sources { | |
| enum TRUE: Source { | |
| static var defaultValue : Bool {true} | |
| } | |
| enum FALSE: Source { | |
| static var defaultValue : Bool {false} | |
| } | |
| enum EMPTYSTRING: Source { | |
| static var defaultValue : String {""} | |
| } | |
| enum EMPTYLIST<T: List>: Source { | |
| static var defaultValue: T{[]} | |
| } | |
| enum EMPTYDICTIONARY<T: Map>: Source { | |
| static var defaultValue: T {[:]} | |
| } | |
| } | |
| } | |
| extension DefaultValue { | |
| typealias True = WrappedValue<Sources.TRUE> | |
| typealias False = WrappedValue<Sources.FALSE> | |
| typealias EmptyString = WrappedValue<Sources.EMPTYSTRING> | |
| typealias EmptyList<T: List> = WrappedValue<Sources.EMPTYLIST<T>> | |
| typealias EmptyDictionary<T: Map> = WrappedValue<Sources.EMPTYDICTIONARY<T>> | |
| } | |
| ////EXAMPLE MODEL | |
| struct Article: Decodable { | |
| var name: String | |
| @DefaultValue.True var isAvailable: Bool | |
| @DefaultValue.False var isFavourite: Bool | |
| @DefaultValue.EmptyString var author: String | |
| @DefaultValue.EmptyList var versions: [String] | |
| @DefaultValue.EmptyDictionary var availableUserTag : [String: String] | |
| } | |
| // 'isAvailable' , 'versions' keys are not available | |
| let items = ["name": "Gagan", "isFavourite": true, "author" : "Ggaan", "versions": ["1","2","3"], "availableUserTag": ["key": "value"]] as [String : AnyObject] | |
| let jsonData = try! JSONSerialization.data(withJSONObject: items, options: .prettyPrinted) | |
| let decoded = JSONDecoder().decode(Article.self, from: jsonData) | |
| print(decoded) |
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