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。

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

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如果我打印 jsonResult，以下是输出

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["Code": 00, "Desc": success, "iinData": <__NSArrayM 0x1c02531a0>\n{\n  name = \xe2\x80\x9cAAA\xe2\x80\x9d;\n  iin = 123456;\n  isOn = 0;\n},\n{\n  name = "Allahabad Bank";\n  iin = 608112;\n  isOn = 0;\n},\n)\n

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我可以将Code、Desc插入 Entity1 中，但如何将 innData 插入 Entity2 中。

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实体 1 结构 实体 2 结构

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以下是将 JSON 结果插入核心数据的代码

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func createEntity1From(dictionary: [String: AnyObject]) -> NSManagedObject? {\n    let context = CoreDataStack.sharedInstance.persistentContainer.viewContext\n    if let Entity1 = NSEntityDescription.insertNewObject(forEntityName: \xe2\x80\x9cParamDownload\xe2\x80\x9d, into: context) as? ParamDownload {\n        Entity1.Code= dictionary[\xe2\x80\x9cname\xe2\x80\x9d] as? String\n        Entity1.desc = dictionary[\xe2\x80\x9cdesc\xe2\x80\x9d] as? String\n        return Entity1\n    }\n}\n

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Answer 1

将 JSON 直接解码为 Core Data 非常容易Decodable

• 首先创建 的扩展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）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）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，请使用便利的初始值设定项创建解码器

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

这init处理关系。

我建议尽可能多地声明核心数据属性的非可选属性。
如果属性必须保持可选，则替换decode为decodeIfPresent.