如何使用 Swift Decodable 映射来自 UUID 键数组的关系?

Question

我有一个结构，其中：

Factories有很多Cards;

而且，players可以有很多Cards(未实现(;它们是相同的卡。

用于测试和内部完整性检查;我想暂时将卡片数组保留在其自己的 JSON 数组中。

所以我想出的结构是这样的：

// Example JSON
{
"factories": [
{
"id": "7a24a713-c0aa-4498-....",
"name": "Steel Factory",
"cost": 4,
"references": [
{ "id": "e936b897-c203-44a5-9cf0-27720f655b68" },
{ "id": "da35424a-6546-4c72-a51c-1f6abfd601a3" }
],
...
"cards": [
{ "id": "e936b897-c203-44a5-9cf0-27720f655b68", name: "Card #1", cost: 4 }
{ "id": "da35424a-6546-4c72-a51c-1f6abfd601a3", name: "Card #2", cost: 4 }
] 
...
}

注意

工厂JSON结构没有cards;解码时它被认为是一个空数组

<小时 />

用例：

根据

匹配的 UUID 键填充工厂卡数组(初始化时为空(，引用的内容<</p>

---

Swift 结构体是：

struct Factory: Codable, Identifiable, Equatable, Hashable {
let id: UUID
let name: String
let cost: Int
var cards: [Card]? 
internal var references: [Reference]?
private enum CodingKeys: String, CodingKey {
case id, name, cost, references
}
}
struct Reference: Codable, Identifiable, Hashable, Equatable {
var id: UUID
private enum CodingKeys: String, CodingKey {
case id
}
}
struct Card: Codable, Identifiable, Hashable, Equatable {
var id: UUID 
var name: String
var cost: Int
private enum CodingKeys: String, CodingKey {
case id, name, cost
}
}

所以，尝试这样做;我已经为每个结构写出了自定义initWithCoder。

extension Reference {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(UUID.self, forKey: .id)
}
}

extension Factory {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(UUID.self, forKey: .id)
name = try container.decode(String.self, forKey: .name)
cost = try container.decode(Int.self, forKey: .cost)
cards = try container.decodeIfPresent([Card].self, forKey: .cards) ?? [Card]()
references = try container.decode([Reference].self, forKey: .references)
}
}
extension Card {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(UUID.self, forKey: .id)
name = try container.decode(String.self, forKey: .name)
cost = try container.decode(String.self, forKey: .cost)
}
}

我想做这样的事情：

// Factory decoder 
references = try container.decode([Reference].self, forKey: .references)
// Find all cards that match the reference ID
// add the matched cards to this factories cards array
let matchedCards: [Card]? = references.map { $0  }
print ("matchedCards")

但是我不确定将 $0 映射到什么，因为 Card 结构无法通过此结构直接访问。

我知道我可以把卡片作为子数组放在工厂结构内。

但我正在考虑，将来可能会有一个桥接结构，其中包含关键引用，例如one to many throughJSON 结构。

我感谢提供的任何反馈。

Answer 1

let referenceIds:[String] = references.map { $0.id }
let decodedCards = container.decode([Card].self, forKey: .cards)
let matchedCards[Card] = decodedCards.filter(where: { referenceIds.contains($0.id)})
self.cards = matchedCards // factory.cards