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Swift 4
Codable
2017/06/19 CA.swift #3 WWDC17ใࠂձ
Yasuhiro Inami / @inamiy
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Session 212
What's New in Foundation
https://developer.apple.com/videos/play/
wwdc2017/212/
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Swift 4 Codable*
Conversion between
Swift data structure and archived formats
* swift-DEVELOPMENT-SNAPSHOT-2017-06-17-a (Xcode 9 Beta 1ʙ) ݱࡏ
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[SE-0166] Swift Archival &
Serialization
[SE-0167] Swift Encoders
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Codable ͷྫ
// JSON
{
"int": 0,
"float": 1.5,
"double": 3.25,
"string": "Swift",
"array": [ "Hello", "World" ],
"dict": { "WWDC": 2017 },
"date": 1496682000,
}
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! [SE-0168] Multi-Line String Literals
let json = """
{
"int": 0,
"float": 1.5,
"double": 3.25,
"string": "Swift",
"array": [ "Hello", "World" ],
"dict": { "WWDC": 2017 },
"date": 1496682000,
}
""".data(using: .utf8)!
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struct MyData: Codable {
let int: Int
let float: Float
let double: Double
let string: String
let array: [String]
let dict: [String: Int]
let date: Date
}
protocol Codable Λ࠾༻͢Δ͚ͩͰɾɾɾ
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let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .secondsSince1970
let decoded = try decoder.decode(MyData.self, from: json)
// MyData(int: 0, float: 1.5, double: 3.25, string: "Swift",
// array: ["Hello", "World"], dict: ["WWDC": 2017],
// date: 2017-06-05 17:00:00 +0000)
let encoder = JSONEncoder()
encoder.dateEncodingStrategy = .secondsSince1970
let encodedData = try encoder.encode(decoded)
let encodedString = String(data: encodedData, encoding: .utf8)!
// {"double":3.25,"int":0,"string":"Swift","date":1496682000,
// "array":["Hello","World"],"float":1.5,"dict":{"WWDC":2017}}
σίʔυɾΤϯίʔυॲཧ͕؆୯ʂ
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ϏϧτΠϯͷ Decoder/Encoder
• JSON(De|En)coder ... JSONSerializationΛ༻
• date(De|En)codingStrategy
• data(De|En)codingStrategy
• nonConformingFloat(De|En)codingStrategy
• PropertyList(De|En)coder ... PropertyListSerializationΛ
༻
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ϏϧτΠϯͷ Codableܕ
• Swift ͷجຊσʔλܕ
• Bool, Int, Int(N), UInt(N), Float, Double, String,
RawRepresentable, Optional, Array, Set, Dictionary
• Foundation / CoreGraphics ͷσʔλܕ
• AffineTransform, Calendar, CharacterSet, Data, Date,
DateComponents, DateInterval, Decimal, IndexPath,
IndexSet, Locale, Measurement, NSRange,
PersonNameComponents, TimeZone, URL, UUID, CGFloat
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Q. Ͳ͏ͬͯຐ๏Λ࣮ݱ
͍ͯ͠Δ!ʁ
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A. ίϯύΠϥʹΑΔ
ࣗಈੜ
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struct User: Codable {
var userName: String
var score: Int
@derived private enum CodingKeys: String, CodingKey { // @derived = ࣗಈੜ
case userName
case score
}
@derived init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
userName = try container.decode(String.self, forKey: .userName)
score = try container.decode(Int.self, forKey: .score)
}
@derived func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(userName, forKey: .userName)
try container.encode(score, forKey: .score)
}
}
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struct User: Codable {
var userName: String // JSON "user_name"ΩʔΛ͍࣋ͬͯΔ
var score: Int // 0...100 ͷΈʹݶఆ͍ͨ͠
private enum CodingKeys: String, CodingKey { // declare explicitly
case userName = "user_name"
case score
}
init(from decoder: Decoder) throws { // declare explicitly
let container = try decoder.container(keyedBy: CodingKeys.self)
score = try container.decode(Int.self, forKey: .score)
guard (0...100).contains(score) else { // validation
throw DecodingError.dataCorrupted(
codingPath: container.codingPath + [CodingKeys.score],
debugDescription: "score is not in range 0...100"
)
}
userName = try container.decode(String.self, forKey: .userName)
}
}
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Codable
ϓϩτίϧ ˍ ܕͷશମ૾
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public typealias Codable = Encodable & Decodable
public protocol Decodable {
init(from decoder: Decoder) throws
}
public protocol Encodable {
func encode(to encoder: Encoder) throws
}
public protocol CodingKey {
public var stringValue: String { get }
public init?(stringValue: String)
public var intValue: Int? { get }
public init?(intValue: Int)
}
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public protocol Decoder {
var codingPath: [CodingKey?] { get }
var userInfo: [CodingUserInfoKey : Any] { get }
func container(keyedBy type: Key.Type) throws
-> KeyedDecodingContainer
func unkeyedContainer() throws -> UnkeyedDecodingContainer
func singleValueContainer() throws -> SingleValueDecodingContainer
}
public protocol Encoder {
var codingPath: [CodingKey?] { get }
var userInfo: [CodingUserInfoKey : Any] { get }
func container(keyedBy type: Key.Type)
-> KeyedEncodingContainer
func unkeyedContainer() -> UnkeyedEncodingContainer
func singleValueContainer() -> SingleValueEncodingContainer
}
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public protocol KeyedDecodingContainerProtocol {
associatedtype Key : CodingKey
var codingPath: [CodingKey?] { get }
var allKeys: [Key] { get }
func contains(_ key: Key) -> Bool
func decode(_ type: T.Type, forKey key: Key) throws -> T
func decodeIfPresent
(_ type: T.Type, forKey key: Key) throws -> T?
func nestedContainer
(keyedBy type: NestedKey.Type, forKey key: Key) throws
-> KeyedDecodingContainer
func nestedUnkeyedContainer(forKey key: Key) throws
-> UnkeyedDecodingContainer
func superDecoder() throws -> Decoder
func superDecoder(forKey key: Key) throws -> Decoder
...
}
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public protocol KeyedEncodingContainerProtocol {
associatedtype Key : CodingKey
var codingPath: [CodingKey?] { get }
mutating func encode(_ value: T, forKey key: Key) throws
mutating func encodeWeak
(_ object: T, forKey key: Key) throws
mutating func encodeIfPresent
(_ value: T?, forKey key: Key) throws
mutating func nestedContainer
(keyedBy keyType: NestedKey.Type, forKey key: Key)
-> KeyedEncodingContainer
mutating func nestedUnkeyedContainer(forKey key: Key)
-> UnkeyedEncodingContainer
mutating func superEncoder() -> Encoder
mutating func superEncoder(forKey key: Key) -> Encoder
...
}
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public protocol UnkeyedDecodingContainer {
var codingPath: [CodingKey?] { get }
var count: Int? { get }
var isAtEnd: Bool { get }
mutating func decode(_ type: T.Type) throws -> T
mutating func decodeIfPresent
(_ type: T.Type) throws -> T?
mutating func nestedContainer
(keyedBy type: NestedKey.Type) throws
-> KeyedDecodingContainer
mutating func nestedUnkeyedContainer() throws
-> UnkeyedDecodingContainer
mutating func superDecoder() throws -> Decoder
...
}
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public protocol UnkeyedEncodingContainer {
var codingPath: [CodingKey?] { get }
mutating func encode(_ value: T) throws
mutating func encodeWeak
(_ object: T) throws
mutating func encode(contentsOf sequence: T) throws
where T.Iterator.Element : Encodable
mutating func nestedContainer
(keyedBy keyType: NestedKey.Type)
-> KeyedEncodingContainer
mutating func nestedUnkeyedContainer() -> UnkeyedEncodingContainer
mutating func superEncoder() -> Encoder
...
}
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public protocol SingleValueDecodingContainer {
public func decodeNil() -> Bool
public func decode(_ type: T.Type) throws -> T
where T : Decodable
...
}
public protocol SingleValueEncodingContainer {
public mutating func encodeNil() throws
public mutating func encode(_ value: T) throws
where T : Encodable
...
}
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public enum DecodingError : Error {
public struct Context {
public let codingPath: [CodingKey?]
public let debugDescription: String
}
case typeMismatch(Any.Type, DecodingError.Context)
case valueNotFound(Any.Type, DecodingError.Context)
case keyNotFound(CodingKey, DecodingError.Context)
case dataCorrupted(DecodingError.Context)
}
public enum EncodingError : Error {
public struct Context {
public let codingPath: [CodingKey?]
public let debugDescription: String
}
case invalidValue(Any, EncodingError.Context)
}
public struct CodingUserInfoKey : RawRepresentable, Equatable, Hashable {
public typealias RawValue = String
}
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ϓϩτίϧ ˍ ܕͷશମ૾ (1)
• CodingKey
• ܕ҆શͳStringΩʔʢIntΩʔՄʣ
• superDecoder/superEncoder
• εʔύʔΫϥεʹ͢༻ʢͪΌΜͱಈ͍ͯΔʁʣ
• Τϥʔॲཧ (DecodingError/EncodingError)
• codingPathΛهͯ͠ɺΤϥʔՕॴͷৄࡉΛग़ྗ
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ϓϩτίϧ ˍ ܕͷશମ૾ (2)
• (Keyed|Unkeyed|SingleValue)(De|En)codingContainer
• (De|En)coder ͕ (de|en)code ॲཧ͢ΔΘΓʹɺ֤
Container͕୲
• (JSONSerializationʹΑΔ) தؒදݱ͕ [String:
Any] ͷͨΊɺunbox/box-ingͰܕ҆શʹॲཧ͢ΔͨΊʹ
Container͕ඞཁ
• [SE-0143] ConditionalConformancesʹΑΔվળͷ༨
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Q. ίϯύΠϥ
Ͳ͏ͬͯ
ॲཧ͍ͯ͠Δʁ!
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// include/swift/AST/KnownProtocols.(h|def)
enum class KnownProtocolKind : uint8_t {
...
CodingKey,
Encodable,
Decodable,
};
// include/swift/AST/(ASTContext.h|KnownIdentifiers.def)
class ASTContext {
...
Identifier Id_CodingKeys,
Identifier Id_Decodable,
Identifier Id_decode,
Identifier Id_decodeIfPresent,
Identifier Id_Decoder,
Identifier Id_decoder,
Identifier Id_superDecoder,
}
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static EnumDecl *synthesizeCodingKeysEnum(TypeChecker &tc,
NominalTypeDecl *target,
ProtocolDecl *proto) {
auto &C = tc.Context;
auto *codingKeyProto = C.getProtocol(KnownProtocolKind::CodingKey);
auto *codingKeyType = codingKeyProto->getDeclaredType();
TypeLoc protoTypeLoc[1] = {TypeLoc::withoutLoc(codingKeyType)};
MutableArrayRef inherited = C.AllocateCopy(protoTypeLoc);
auto *enumDecl = new (C) EnumDecl(SourceLoc(), C.Id_CodingKeys, SourceLoc(),
inherited, nullptr, target);
enumDecl->setImplicit();
enumDecl->setAccessibility(Accessibility::Private);
// `private enum CodingKeys: CodingKey` Λੜ
...
return enumDecl
}
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// lib/Sema/DerivedConformanceCodable.cpp
// lib/Sema/DerivedConformanceCodingKey.cpp
/// `init(from decoder: Decoder) throws`͕ແ͍߹ɺࣗಈੜ
static void deriveBodyDecodable_init(...)
/// `func encode(to encoder: Encoder) throws`͕ແ͍߹ɺࣗಈੜ
static void deriveBodyEncodable_encode(...)
/// `private enum CodingKeys: CodingKey`͕ແ͍߹ɺҰ͔Β࡞Δ
static EnumDecl *synthesizeCodingKeysEnum(...)
/// `enum CodingKey: CodingKey`͕͋Δ߹ɺ
/// `var stringValue: String`Λࣗಈੜ
ValueDecl *DerivedConformance::deriveCodingKey(...)
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CodableͰؾʹͳͬͨ
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ܕม͕ඞཁ
let myData: MyData
let decoder = JSONDecoder()
myData = try decoder.decode(MyData.self, from: json)
ฦΓΛܕਪͤͨ͞ํ͕γϯϓϧˍԠ༻͕ޮ͘ͷͰʁ
myData = try decoder.decode(from: json)
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https://twitter.com/dgregor79/status/873960672060514304
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static bool validateCodingKeysEnum(TypeChecker &tc, EnumDecl *codingKeysDecl,
NominalTypeDecl *target, ProtocolDecl *proto) {
llvm::SmallDenseMap properties;
for (auto *varDecl : target->getStoredProperties(/*skipInaccessible=*/true)) {
properties[varDecl->getName()] = varDecl;
}
// Codable ͷ stored properties ͱ CodingKey ͷ cases Λൺֱͯ͠ɺ1ର1ରԠ͔Ͳ͏͔ΛνΣοΫ
bool propertiesAreValid = true;
for (auto elt : codingKeysDecl->getAllElements()) {
auto it = properties.find(elt->getName());
if (it == properties.end()) {
tc.diagnose(elt->getLoc(), diag::codable_extraneous_codingkey_case_here,
elt->getName());
propertiesAreValid = false;
continue;
}
...
}
if (!propertiesAreValid)
return false;
...
}
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Q. Codable ͷ Stored properties ͱ
CodingKey cases ͕
1ର1ରԠ͠ͳ͍߹ʁ!
(ྫɿMyCodableͷ͋ΔϓϩύςΟΛ"ෳͷΩʔͷ"͔Βࢉग़͍ͨ͠ɺͳͲ)
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ʢ͍ͬͯΔਓ͍ͨΒڭ͍͑ͯͩ͘͞ʣ
!
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·ͱΊ
• Codable Appleެࣜͷຐ๏
• 3ʹΔSwift JSONϥΠϒϥϦઓ૪ʹऴࢭූ
• ͱ͍͑ɺContainer + CodingKey ͷखಈ࣮໘
• ॴײ
• Containerɺܕ҆શͰͳ͍چ࣌ͷͨΊͷworkaround
• CodingKeyͷ1:1ରԠɺएׯΓ͗͢ʁ
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ͱ͍͑ɺAPI៉ྷͩ͠ɺ
CodableʹରԠ͢Ε
৭ʑͳ(De|En)coderʹ
ରԠͰ͖Δ!
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Thanks!
Yasuhiro Inami
@inamiy