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カスタムSwift Strings Resource Formatのエンコーダー/デコーダー

私はCodableをいじくり回し、JSONをファイルとの間で読み書きしています。次に、iOSを読み書きできるカスタムCoderを作成したい.stringsファイル。誰もこれで私を助けることができますか？プロトコルEncoderおよびDecoderが見つかりましたが、ここで何を実装する必要があるのか​​わかりません。

class StringsEncoder {}

extension StringsEncoder: Encoder {
    var codingPath: [CodingKey?] {
        return []
    }

    var userInfo: [CodingUserInfoKey : Any] {
        return [:]
    }

    func container<Key>(keyedBy type: Key.Type) -> KeyedEncodingContainer<Key> where Key : CodingKey {

    }

    func unkeyedContainer() -> UnkeyedEncodingContainer {

    }

    func singleValueContainer() -> SingleValueEncodingContainer {

    }
}

extension StringsEncoder: Decoder {
    func container<Key>(keyedBy type: Key.Type) throws -> KeyedDecodingContainer<Key> where Key : CodingKey {

    }

    func unkeyedContainer() throws -> UnkeyedDecodingContainer {

    }

    func singleValueContainer() throws -> SingleValueDecodingContainer {

    }
}
swiftswift4codabledecodableencodable
34
Banana

ここでのパーティーに少し遅れましたが、これは、票数が多いという質問を考えると、他の人にとって有益/有益かもしれないと感じています。 （しかし、私は実際にそのようなコードの実際の有用性に実際に入るwo n'tそれについては上記のコメントをチェックしてください。）

残念ながら、コーディングスタックの柔軟性と型安全性を考えると、新しいencodingおよびdecodingソリューションを実装することは、代替のexternal representationにはほど遠い簡単なタスク...

エンコーディング

まず、目的の stringsファイル 外部表現にencoding部分を実装することから始めましょう。 （必要なタイプは、トップダウン方式で導入されます。）

標準のJSONEncoderクラスと同様に、新しいエンコーディングAPIを公開/駆動するクラスを導入する必要があります。それをStringsEncoderと呼びましょう：

/// An object that encodes instances of a data type 
/// as strings following the simple strings file format.
public class StringsEncoder {

    /// Returns a strings file-encoded representation of the specified value. 
    public func encode<T: Encodable>(_ value: T) throws -> String {
        let stringsEncoding = StringsEncoding()
        try value.encode(to: stringsEncoding)
        return dotStringsFormat(from: stringsEncoding.data.strings)
    }

    private func dotStringsFormat(from strings: [String: String]) -> String {
        var dotStrings = strings.map { "\"\($0)\" = \"\($1)\";" }
        dotStrings.sort()
        dotStrings.insert("/* Generated by StringsEncoder */", at: 0)
        return dotStrings.joined(separator: "\n")
    }
}

次に、コアstructプロトコルに準拠するタイプ（たとえば、Encoder）を提供する必要があります。

fileprivate struct StringsEncoding: Encoder {

    /// Stores the actual strings file data during encoding.
    fileprivate final class Data {
        private(set) var strings: [String: String] = [:]

        func encode(key codingKey: [CodingKey], value: String) {
            let key = codingKey.map { $0.stringValue }.joined(separator: ".")
            strings[key] = value
        }
    }

    fileprivate var data: Data

    init(to encodedData: Data = Data()) {
        self.data = encodedData
    }

    var codingPath: [CodingKey] = []

    let userInfo: [CodingUserInfoKey : Any] = [:]

    func container<Key: CodingKey>(keyedBy type: Key.Type) -> KeyedEncodingContainer<Key> {
        var container = StringsKeyedEncoding<Key>(to: data)
        container.codingPath = codingPath
        return KeyedEncodingContainer(container)
    }

    func unkeyedContainer() -> UnkeyedEncodingContainer {
        var container = StringsUnkeyedEncoding(to: data)
        container.codingPath = codingPath
        return container
   }

    func singleValueContainer() -> SingleValueEncodingContainer {
        var container = StringsSingleValueEncoding(to: data)
        container.codingPath = codingPath
        return container
    }
}

最後に、3つのすべてのエンコードコンテナータイプを処理する必要があります。

  • KeyedEncodingContainer
  • UnkeyedEncodingContainer
  • SingleValueEncodingContainer
fileprivate struct StringsKeyedEncoding<Key: CodingKey>: KeyedEncodingContainerProtocol {

    private let data: StringsEncoding.Data

    init(to data: StringsEncoding.Data) {
        self.data = data
    }

    var codingPath: [CodingKey] = []

    mutating func encodeNil(forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: "nil")
    }

    mutating func encode(_ value: Bool, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: String, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value)
    }

    mutating func encode(_ value: Double, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: Float, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: Int, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: Int8, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: Int16, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: Int32, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: Int64, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: UInt, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: UInt8, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: UInt16, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: UInt32, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode(_ value: UInt64, forKey key: Key) throws {
        data.encode(key: codingPath + [key], value: value.description)
    }

    mutating func encode<T: Encodable>(_ value: T, forKey key: Key) throws {
        var stringsEncoding = StringsEncoding(to: data)
        stringsEncoding.codingPath.append(key)
        try value.encode(to: stringsEncoding)
    }

    mutating func nestedContainer<NestedKey: CodingKey>(
        keyedBy keyType: NestedKey.Type,
        forKey key: Key) -> KeyedEncodingContainer<NestedKey> {
        var container = StringsKeyedEncoding<NestedKey>(to: data)
        container.codingPath = codingPath + [key]
        return KeyedEncodingContainer(container)
    }

    mutating func nestedUnkeyedContainer(forKey key: Key) -> UnkeyedEncodingContainer {
        var container = StringsUnkeyedEncoding(to: data)
        container.codingPath = codingPath + [key]
        return container
    }

    mutating func superEncoder() -> Encoder {
        let superKey = Key(stringValue: "super")!
        return superEncoder(forKey: superKey)
    }

    mutating func superEncoder(forKey key: Key) -> Encoder {
        var stringsEncoding = StringsEncoding(to: data)
        stringsEncoding.codingPath = codingPath + [key]
        return stringsEncoding
    }
}

fileprivate struct StringsUnkeyedEncoding: UnkeyedEncodingContainer {

    private let data: StringsEncoding.Data

    init(to data: StringsEncoding.Data) {
        self.data = data
    }

    var codingPath: [CodingKey] = []

    private(set) var count: Int = 0

    private mutating func nextIndexedKey() -> CodingKey {
        let nextCodingKey = IndexedCodingKey(intValue: count)!
        count += 1
        return nextCodingKey
    }

    private struct IndexedCodingKey: CodingKey {
        let intValue: Int?
        let stringValue: String

        init?(intValue: Int) {
            self.intValue = intValue
            self.stringValue = intValue.description
        }

        init?(stringValue: String) {
            return nil
        }
    }

    mutating func encodeNil() throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: "nil")
    }

    mutating func encode(_ value: Bool) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: String) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value)
    }

    mutating func encode(_ value: Double) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: Float) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: Int) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: Int8) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: Int16) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: Int32) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: Int64) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: UInt) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: UInt8) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: UInt16) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: UInt32) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode(_ value: UInt64) throws {
        data.encode(key: codingPath + [nextIndexedKey()], value: value.description)
    }

    mutating func encode<T: Encodable>(_ value: T) throws {
        var stringsEncoding = StringsEncoding(to: data)
        stringsEncoding.codingPath = codingPath + [nextIndexedKey()]
        try value.encode(to: stringsEncoding)
    }

    mutating func nestedContainer<NestedKey: CodingKey>(
        keyedBy keyType: NestedKey.Type) -> KeyedEncodingContainer<NestedKey> {
        var container = StringsKeyedEncoding<NestedKey>(to: data)
        container.codingPath = codingPath + [nextIndexedKey()]
        return KeyedEncodingContainer(container)
    }

    mutating func nestedUnkeyedContainer() -> UnkeyedEncodingContainer {
        var container = StringsUnkeyedEncoding(to: data)
        container.codingPath = codingPath + [nextIndexedKey()]
        return container
    }

    mutating func superEncoder() -> Encoder {
        var stringsEncoding = StringsEncoding(to: data)
        stringsEncoding.codingPath.append(nextIndexedKey())
        return stringsEncoding
    }
}

fileprivate struct StringsSingleValueEncoding: SingleValueEncodingContainer {

    private let data: StringsEncoding.Data

    init(to data: StringsEncoding.Data) {
        self.data = data
    }

    var codingPath: [CodingKey] = []

    mutating func encodeNil() throws {
        data.encode(key: codingPath, value: "nil")
    }

    mutating func encode(_ value: Bool) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: String) throws {
        data.encode(key: codingPath, value: value)
    }

    mutating func encode(_ value: Double) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: Float) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: Int) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: Int8) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: Int16) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: Int32) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: Int64) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: UInt) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: UInt8) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: UInt16) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: UInt32) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode(_ value: UInt64) throws {
        data.encode(key: codingPath, value: value.description)
    }

    mutating func encode<T: Encodable>(_ value: T) throws {
        var stringsEncoding = StringsEncoding(to: data)
        stringsEncoding.codingPath = codingPath
        try value.encode(to: stringsEncoding)
    }
}

明らかに、（非常に！）シンプルなstrings file形式を使用して、ネストされた型をエンコードする方法に関して、いくつかの設計上の決定を下しました。うまくいけば、私のコードが十分に明確であり、必要に応じてエンコードの詳細を簡単に調整できるはずです。

テスト

単純なCodable型の簡単なテスト：

struct Product: Codable {
    var name: String
    var price: Float
    var info: String
}

let iPhone = Product(name: "iPhone X", price: 1_000, info: "Our best iPhone yet!")

let stringsEncoder = StringsEncoder()
do {
    let stringsFile = try stringsEncoder.encode(iPhone)
    print(stringsFile)
} catch {
    print("Encoding failed: \(error)")
}

出力：

/* Generated by StringsEncoder */
"info" = "Our best iPhone yet!";
"name" = "iPhone X";
"price" = "1000.0";

nested structsおよびarraysを使用したより複雑なテスト：

struct Product: Codable {
    var name: String
    var price: Float
    var info: String
}

struct Address: Codable {
    var street: String
    var city: String
    var state: String
}

struct Store: Codable {
    var name: String
    var address: Address // nested struct
    var products: [Product] // array
}

let iPhone = Product(name: "iPhone X", price: 1_000, info: "Our best iPhone yet!")
let macBook = Product(name: "Mac Book Pro", price: 2_000, info: "Early 2019")
let watch = Product(name: "Apple Watch", price: 500, info: "Series 4")

let appleStore = Store(
    name: "Apple Store",
    address: Address(street: "300 Post Street", city: "San Francisco", state: "CA"),
    products: [iPhone, macBook, watch]
)

let stringsEncoder = StringsEncoder()
do {
    let stringsFile = try stringsEncoder.encode(appleStore)
    print(stringsFile)
} catch {
    print("Encoding failed: \(error)")
}

出力：

/* Generated by StringsEncoder */
"address.city" = "San Francisco";
"address.state" = "CA";
"address.street" = "300 Post Street";
"name" = "Apple Store";
"products.0.info" = "Our best iPhone yet!";
"products.0.name" = "iPhone X";
"products.0.price" = "1000.0";
"products.1.info" = "Early 2019";
"products.1.name" = "Mac Book Pro";
"products.1.price" = "2000.0";
"products.2.info" = "Series 4";
"products.2.name" = "Apple Watch";
"products.2.price" = "500.0";

デコード

この答えがすでにどれだけ大きいかを考えて、decoding部分を残します（つまり、StringsDecoderクラスを作成して、 Decoderプロトコルなど）読者への演習として...皆さんがそれに関して何か助けが必要かどうか教えてください;）

10
Paulo Mattos