//
// EmptyObjectDecoder.swift
// JSONAPI
//
// Created by Mathew Polzin on 7/2/19.
//
/// `EmptyObjectDecoder` exists internally for the sole purpose of
/// allowing certain fallback logic paths to attempt to create `Decodable`
/// types from empty containers (specifically in a way that is agnostic
/// of any given encoding). In other words, this serves the same purpose
/// as `JSONDecoder().decode(Thing.self, from: "{}".data(using: .utf8)!)`
/// without needing to use a third party or `Foundation` library decoder.
struct EmptyObjectDecoder: Decoder {
var codingPath: [CodingKey] = []
var userInfo: [CodingUserInfoKey : Any] = [:]
func container(keyedBy type: Key.Type) throws -> KeyedDecodingContainer where Key : CodingKey {
return KeyedDecodingContainer(EmptyKeyedContainer())
}
func unkeyedContainer() throws -> UnkeyedDecodingContainer {
return EmptyUnkeyedContainer()
}
func singleValueContainer() throws -> SingleValueDecodingContainer {
throw EmptyObjectDecodingError.emptyObjectCannotBeSingleValue
}
}
enum EmptyObjectDecodingError: Swift.Error {
case emptyObjectCannotBeSingleValue
case emptyObjectCannotBeUnkeyedValues
case emptyObjectCannotHaveKeyedValues
case emptyObjectCannotHaveNestedContainers
case emptyObjectCannotHaveSuper
}
struct EmptyUnkeyedContainer: UnkeyedDecodingContainer {
var codingPath: [CodingKey] { return [] }
var count: Int? { return 0 }
var isAtEnd: Bool { return true }
var currentIndex: Int { return 0 }
mutating func decodeNil() throws -> Bool {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Bool.Type) throws -> Bool {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: String.Type) throws -> String {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Double.Type) throws -> Double {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Float.Type) throws -> Float {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Int.Type) throws -> Int {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Int8.Type) throws -> Int8 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Int16.Type) throws -> Int16 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Int32.Type) throws -> Int32 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: Int64.Type) throws -> Int64 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: UInt.Type) throws -> UInt {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: UInt8.Type) throws -> UInt8 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: UInt16.Type) throws -> UInt16 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: UInt32.Type) throws -> UInt32 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: UInt64.Type) throws -> UInt64 {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func decode(_ type: T.Type) throws -> T where T : Decodable {
throw EmptyObjectDecodingError.emptyObjectCannotBeUnkeyedValues
}
mutating func nestedContainer(keyedBy type: NestedKey.Type) throws -> KeyedDecodingContainer where NestedKey : CodingKey {
throw EmptyObjectDecodingError.emptyObjectCannotHaveNestedContainers
}
mutating func nestedUnkeyedContainer() throws -> UnkeyedDecodingContainer {
throw EmptyObjectDecodingError.emptyObjectCannotHaveNestedContainers
}
mutating func superDecoder() throws -> Decoder {
throw EmptyObjectDecodingError.emptyObjectCannotHaveSuper
}
}
struct EmptyKeyedContainer: KeyedDecodingContainerProtocol {
var codingPath: [CodingKey] { return [] }
var allKeys: [Key] { return [] }
func contains(_ key: Key) -> Bool {
return false
}
func decodeNil(forKey key: Key) throws -> Bool {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Bool.Type, forKey key: Key) throws -> Bool {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: String.Type, forKey key: Key) throws -> String {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Double.Type, forKey key: Key) throws -> Double {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Float.Type, forKey key: Key) throws -> Float {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Int.Type, forKey key: Key) throws -> Int {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Int8.Type, forKey key: Key) throws -> Int8 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Int16.Type, forKey key: Key) throws -> Int16 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Int32.Type, forKey key: Key) throws -> Int32 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: Int64.Type, forKey key: Key) throws -> Int64 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: UInt.Type, forKey key: Key) throws -> UInt {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: UInt8.Type, forKey key: Key) throws -> UInt8 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: UInt16.Type, forKey key: Key) throws -> UInt16 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: UInt32.Type, forKey key: Key) throws -> UInt32 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: UInt64.Type, forKey key: Key) throws -> UInt64 {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func decode(_ type: T.Type, forKey key: Key) throws -> T where T : Decodable {
throw EmptyObjectDecodingError.emptyObjectCannotHaveKeyedValues
}
func nestedContainer(keyedBy type: NestedKey.Type, forKey key: Key) throws -> KeyedDecodingContainer where NestedKey : CodingKey {
throw EmptyObjectDecodingError.emptyObjectCannotHaveNestedContainers
}
func nestedUnkeyedContainer(forKey key: Key) throws -> UnkeyedDecodingContainer {
throw EmptyObjectDecodingError.emptyObjectCannotHaveNestedContainers
}
func superDecoder() throws -> Decoder {
throw EmptyObjectDecodingError.emptyObjectCannotHaveSuper
}
func superDecoder(forKey key: Key) throws -> Decoder {
throw EmptyObjectDecodingError.emptyObjectCannotHaveSuper
}
}