Swift&Codable：如何“繞過”一些JSON級別？

我想使用這個 Pokémon API來獲取一些資料并將其轉換為 SwiftPokemon結構。

這是我在獲取 Pokemon #142 時得到的回應的摘錄：

{
    "id": 142,
    "name": "aerodactyl",
    "types": [{
            "type": {
                "name": "rock",
                "url": "https://pokeapi.co/api/v2/type/6/"
            },
            "slot": 1
        },
        {
            "type": {
                "name": "flying",
                "url": "https://pokeapi.co/api/v2/type/3/"
            },
            "slot": 2
        }
    ]
}

這是我撰寫的用于將此 JSON 轉換為 Swift 型別的結構：

struct Pokemon: Codable {
    var id: Int
    let name: String
    var types: [PokemonType]?
}

struct PokemonType: Codable {
    var type: PokemonTypeContent
}

struct PokemonTypeContent: Codable {
    var name: PokemonTypeNameContent
}

enum PokemonTypeNameContent: String, Codable {
    case flying = "flying"
    case rock = "rock"
    // ...
}

現在這是我的問題：當我想獲得口袋妖怪型別時，我需要深入研究：

pokemon.types.first?.type.name

我想知道我是否有一種方法可以PokemonTypeNameContent在結構中獲取陣列Pokemon，以執行以下操作：

struct Pokemon {
    var types: [PokemonTypeNameContent]?
}

（我對獲取slot值不感興趣）。

感謝您的幫助！

uj5u.com熱心網友回復：

您可以對 進行自定義編碼PokemonTypeNameContent，并使用 JSON 遍歷各個級別nestedContainer

enum PokemonTypeNameContent: String, Decodable {
    case flying = "flying"
    case rock = "rock"
    // ...
    
    enum OuterCodingKeys: CodingKey { case type }
    enum InnerCodingKeys: CodingKey { case name }
    
    init(from decoder: Decoder) throws {
        // this is the container for each JSON object in the "types" array
        let container = try decoder.container(keyedBy: OuterCodingKeys.self)

        // this finds the nested container (i.e. JSON object) associated with the key "type"
        let innerContainer = try container.nestedContainer(keyedBy: InnerCodingKeys.self, forKey: .type)

        // now we can decode "name" as a string
        let name = try innerContainer.decode(String.self, forKey: .name)
        if let pokemonType = Self.init(rawValue: name) {
            self = pokemonType
        } else {
            throw DecodingError.typeMismatch(
                PokemonTypeNameContent.self,
                    .init(codingPath: innerContainer.codingPath   [InnerCodingKeys.name],
                          debugDescription: "Unknown pokemon type '\(name)'",
                          underlyingError: nil
                         )
            )
        }
    }
}

// Pokemon can then be declared like this:
struct Pokemon: Decodable {
    let id: Int
    let name: String
    let types: [PokemonTypeNameContent]
}

請注意，這意味著您失去了將解碼PokemonTypeNameContent作為常規列舉的選項。如果您確實想這樣做，請將自定義解碼代碼放入屬性包裝器中。請注意，我們將解碼整個 JSON 陣列，而不是每個 JSON 物件。

@propertyWrapper
struct DecodePokemonTypes: Decodable {
    var wrappedValue: [PokemonTypeNameContent]
    
    init(wrappedValue: [PokemonTypeNameContent]) {
        self.wrappedValue = wrappedValue
    }
    
    enum OuterCodingKeys: CodingKey { case type }
    enum InnerCodingKeys: CodingKey { case name }
    
    init(from decoder: Decoder) throws {
        // container for the "types" JSON array
        var unkeyedContainer = try decoder.unkeyedContainer()
        wrappedValue = []

        // while we are not at the end of the JSON array
        while !unkeyedContainer.isAtEnd {

            // similar to the first code snippet
            let container = try unkeyedContainer.nestedContainer(keyedBy: OuterCodingKeys.self)
            let innerContainer = try container.nestedContainer(keyedBy: InnerCodingKeys.self, forKey: .type)
            let name = try innerContainer.decode(String.self, forKey: .name)
            if let pokemonType = PokemonTypeNameContent(rawValue: name) {
                wrappedValue.append(pokemonType)
            } else {
                throw DecodingError.typeMismatch(
                    PokemonTypeNameContent.self,
                        .init(codingPath: innerContainer.codingPath   [InnerCodingKeys.name],
                              debugDescription: "Unknown pokemon type '\(name)'",
                              underlyingError: nil
                             )
                )
            }
        }
    }
}

// You would write this in Pokemon
@DecodePokemonTypes
var types: [PokemonTypeNameContent]

標籤：json 迅速 可编码

上一篇：本地化UIButtonXcode時字體更改

下一篇：是否可以使用SKScene設定固定選單？