ios - 在 Swift 中将复杂的 JSON 保存到 Core Data

Question

我想将 Web 服务的 JSON 结果保存到核心数据，以下是 JSON 解析的代码。

if let jsonResult = try JSONSerialization.jsonObject(with: JSONData!, options: [.mutableContainers]) as? [String: AnyObject]

如果我打印 jsonResult，以下是输出

["Code": 00, "Desc": success, "iinData": <__NSArrayM 0x1c02531a0>
{
  name = “AAA”;
  iin = 123456;
  isOn = 0;
},
{
  name = "Allahabad Bank";
  iin = 608112;
  isOn = 0;
},
)

我可以将Code, Desc插入到 Entity1 中，但是如何将 innData 插入到 Entity2 中。

Entity1 结构 Entity2 结构

以下是将 JSON 结果插入核心数据的代码

func createEntity1From(dictionary: [String: AnyObject]) -> NSManagedObject? {
    let context = CoreDataStack.sharedInstance.persistentContainer.viewContext
    if let Entity1 = NSEntityDescription.insertNewObject(forEntityName: “ParamDownload”, into: context) as? ParamDownload {
        Entity1.Code= dictionary[“name”] as? String
        Entity1.desc = dictionary[“desc”] as? String
        return Entity1
    }
}

标签： iosjsonswiftcore-data

Answer 1

将 JSON 直接解码为 Core Data 非常容易Decodable

• 首先创建扩展CodingUserInfoKey并JSONDecoder能够传递托管对象上下文

  extension CodingUserInfoKey {
      static let context = CodingUserInfoKey(rawValue: "context")!
  }
  
  extension JSONDecoder {
      convenience init(context: NSManagedObjectContext) {
          self.init()
          self.userInfo[.context] = context
      }
  }
  

• Decodable在两个类中添加一致性

  class Name: NSManagedObject, Decodable {
  
  class ParamDownload: NSManagedObject, Decodable {
  

• 在类Name（不是扩展名）中添加

  private enum CodingKeys: String, CodingKey { case name, iin, isOn }
  
  required convenience init(from decoder: Decoder) throws {
      guard let context = decoder.userInfo[.context] as? NSManagedObjectContext else { fatalError("NSManagedObjectContext is missing") }
      let entity = NSEntityDescription.entity(forEntityName: "Name", in: context)!
      self.init(entity: entity, insertInto: context)
      let values = try decoder.container(keyedBy: CodingKeys.self)
      name = try values.decode(String.self, forKey: .name)
      iin = try values.decode(String.self.self, forKey: .iin)
      isOn = try values.decode(Bool.self.self, forKey: .isOn)
  }
  

• 在类ParamDownload（不是扩展名）中添加

  private enum CodingKeys: String, CodingKey { case code = "Code", desc = "Desc", names = "iinData" }
  
  required convenience init(from decoder: Decoder) throws {
      guard let context = decoder.userInfo[.context] as? NSManagedObjectContext else { fatalError("NSManagedObjectContext is missing") }
      let entity = NSEntityDescription.entity(forEntityName: "ParamDownload", in: context)!
      self.init(entity: entity, insertInto: context)
      let values = try decoder.container(keyedBy: CodingKeys.self)
      code = try values.decode(String.self, forKey: .code)
      desc = try values.decode(String.self, forKey: .desc)
      names = try values.decode(Set<Name>.self, forKey: .names)
      names.forEach { $0.pd = self }
  }
  

要解码 JSON，请使用便利初始化程序创建解码器

let decoder = JSONDecoder(context: CoreDataStack.sharedInstance.persistentContainer.viewContext)

方法处理init关系。

我建议尽可能多地声明 Core Data 属性是非可选的。
如果一个属性必须是可选decode的，用decodeIfPresent.