嵌套容器nil值自定義解碼器Swift

所以我有這個簡單的 json 回應：

{
    "gender": "male",
    "name": {
        "title": "mr",
        "first": "brad",
        "last": "gibson"
        }
}

這是我的客戶解碼器：

struct UserModel: Decodable {
    var gender: String
    var title: String?
    var first: String?
    var last: String?
    
    // Top-level coding keys
    enum CodingKeys: String, CodingKey {
        case name, gender
    }
    
    enum NameKeys: CodingKey {
        case title, first, last
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        gender = try container.decode(String.self, forKey: .gender)
        let name = try container.nestedContainer(keyedBy: NameKeys.self, forKey: .name)
        title = try name.decodeIfPresent(String.self, forKey: .title)
        first = try name.decodeIfPresent(String.self, forKey: .first)
        last = try name.decodeIfPresent(String.self, forKey: .last)
    }
}

如果未發送嵌套物件名稱（title, first, last）中的一個鍵，我知道如何處理錯誤情況。我的問題是，如果“名稱”物件沒有從回應中發回，我將如何撰寫一些東西來防止崩潰？

uj5u.com熱心網友回復：

下面怎么用？

struct Name: Decodable {

    var title: String?
    var first: String?
    var last: String?

}

struct UserModel: Decodable {
    var name: Name?
    var gender: String
}

然后其他一切都會自行處理。例如，以下所有內容都將被決議而不會出現問題。

{
    "gender": "male",
    "name": {
        "title": "mr",
        "first": "brad",
        "last": "gibson"
        }
}

{
    "gender": "male"
}

{
    "gender": "male",
    "name": {
        "title": "mr",
        "first": "brad"
        }
}

我測驗使用下面

let str = """
    {
        "gender": "male",
        "name": {
            "title": "mr",
            "first": "brad"
            }
    }
    """

let usermodel = try! JSONDecoder().decode(UserModel.self, from: str.data(using: .utf8)!)
print(usermodel)

uj5u.com熱心網友回復：

您可以具有嵌套Codable結構，例如：

struct User: Codable {
    let gender: String
    let name: UserName?
}

struct UserName: Codable {
    let title: String?
    let first: String?
    let last: String?
}

為了使語法更好user.name?.title，我們可以將其更改為僅user.title使用@dynamicMemberLookup. 改成User這樣：

@dynamicMemberLookup
struct User: Codable {
    let gender: String
    let name: UserName?

    subscript<T>(dynamicMember k: KeyPath<UserName, T>) -> T? {
        name?[keyPath: k]
    }

    subscript<T>(dynamicMember k: KeyPath<UserName, T?>) -> T? {
        name?[keyPath: k]
    }
}

現在，您可以使用簡寫形式來獲取每個屬性。這現在模擬具有所有屬性的單個容器。

uj5u.com熱心網友回復：

感謝 Deepika，這是解決方案：

struct UserModel: Decodable {
var gender: String
var title: String?
var first: String?
var last: String?

// Top-level coding keys
enum CodingKeys: String, CodingKey {
    case name, gender
}

enum NameKeys: CodingKey {
    case title, first, last
}

init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    gender = try container.decode(String.self, forKey: .gender)
    
    if container.contains(.name) {
        let name = try container.nestedContainer(keyedBy: NameKeys.self, forKey: .name)
        title = try name.decode(String.self, forKey: .title)
        first = try name.decode(String.self, forKey: .first)
        last = try name.decode(String.self, forKey: .last)
    }
}

}

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