Swift4嵌套JSON解析：模型类的编码与解码实现问询

Looks like you're halfway there with your RootClass! Let's finish the implementation and add the missing List struct to handle the nested JSON array. Here's the full, working code:

struct RootClass: Codable {
    let details: String?
    let itemCount: Int?
    let list: [List]?
    
    enum CodingKeys: String, CodingKey {
        case details = "Details"
        case itemCount = "ItemCount"
        case list = "List"
    }
    
    // Completed custom decoder
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        details = try values.decodeIfPresent(String.self, forKey: .details)
        itemCount = try values.decodeIfPresent(Int.self, forKey: .itemCount)
        list = try values.decodeIfPresent([List].self, forKey: .list)
    }
    
    // Optional custom encoder (for converting the model back to JSON)
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encodeIfPresent(details, forKey: .details)
        try container.encodeIfPresent(itemCount, forKey: .itemCount)
        try container.encodeIfPresent(list, forKey: .list)
    }
}

Next, you need to define the List struct that represents each item in the List array from your JSON. I'll use a placeholder example—replace the properties with whatever matches your actual JSON structure:

struct List: Codable {
    let id: Int?
    let name: String?
    let description: String?
    
    // Adjust these keys to match your JSON's actual field names
    enum CodingKeys: String, CodingKey {
        case id = "Id"
        case name = "Name"
        case description = "Description"
    }
    
    // Optional custom decoder (remove if no special logic is needed)
    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        id = try values.decodeIfPresent(Int.self, forKey: .id)
        name = try values.decodeIfPresent(String.self, forKey: .name)
        description = try values.decodeIfPresent(String.self, forKey: .description)
    }
    
    // Optional custom encoder (remove if no special logic is needed)
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encodeIfPresent(id, forKey: .id)
        try container.encodeIfPresent(name, forKey: .name)
        try container.encodeIfPresent(description, forKey: .description)
    }
}

Key Tips to Keep in Mind: #

• CodingKeys: These map your Swift property names to the actual keys in the JSON (case-sensitive!). If your JSON keys match your Swift property names exactly, you can skip the CodingKeys enum entirely—Swift will auto-generate it for you.
• Optional Properties: Using ? means the decoder won't throw an error if those keys are missing from the JSON. If a field is required, remove the ? and use decode() instead of decodeIfPresent().
• Auto-Synthesis: If you don't need custom logic for encoding/decoding, you can omit the init(from:) and encode(to:) methods. Swift will generate them automatically, making your code much cleaner. For example, the RootClass could be simplified to:

  struct RootClass: Codable {
      let details: String?
      let itemCount: Int?
      let list: [List]?
      
      enum CodingKeys: String, CodingKey {
          case details = "Details"
          case itemCount = "ItemCount"
          case list = "List"
      }
  }
  

Example Usage (Decoding JSON): #

Here's how you'd use this model to decode a JSON response from an API or local file:

// Sample JSON data (replace with your actual data)
let jsonString = """
{
    "Details": "Sample order details",
    "ItemCount": 2,
    "List": [
        {
            "Id": 101,
            "Name": "Wireless Headphones",
            "Description": "Noise-cancelling over-ear model"
        },
        {
            "Id": 102,
            "Name": "Portable Charger",
            "Description": "20000mAh fast-charging"
        }
    ]
}
"""

if let jsonData = jsonString.data(using: .utf8) {
    do {
        let rootModel = try JSONDecoder().decode(RootClass.self, from: jsonData)
        print("Order Details: \(rootModel.details ?? "No details provided")")
        print("Total Items: \(rootModel.itemCount ?? 0)")
        rootModel.list?.forEach { item in
            print("- \(item.name ?? "Unnamed Item"): \(item.description ?? "No description")")
        }
    } catch {
        print("Decoding error: \(error.localizedDescription)")
    }
}

内容的提问来源于stack exchange，提问作者stack qstns