JSON Parsing

1. Codable Model

struct User: Codable, Identifiable {
    let id: Int
    let name: String
    let email: String
}

2. Nested JSON

struct Response: Codable {
    let status: String
    let data: DataWrapper
}

struct DataWrapper: Codable {
    let users: [User]
}

// Decode
let response = try JSONDecoder().decode(Response.self, from: data)
let users = response.data.users

3. Custom Keys

struct Post: Codable {
    let id: Int
    let title: String
    let createdAt: Date

    enum CodingKeys: String, CodingKey {
        case id
        case title
        case createdAt = "created_at"
    }
}

4. Date Decoding

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601

// Custom format
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
decoder.dateDecodingStrategy = .formatted(formatter)

5. Snake Case

let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase

6. Optional và Default Values

struct Item: Codable {
    let id: Int
    let name: String
    let description: String?  // Optional

    // Default value
    var quantity: Int = 1

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decode(Int.self, forKey: .id)
        name = try container.decode(String.self, forKey: .name)
        description = try container.decodeIfPresent(String.self, forKey: .description)
        quantity = try container.decodeIfPresent(Int.self, forKey: .quantity) ?? 1
    }
}

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📝 Tóm tắt

Strategy	Mục đích
CodingKeys	Map property names
.convertFromSnakeCase	snake_case → camelCase
.iso8601	Parse ISO dates
decodeIfPresent	Optional values