How to serialize or convert Swift objects to JSON?

Question

This below class

class User: NSManagedObject {
  @NSManaged var id: Int
  @NSManaged var name: String
}

Needs to be converted to

Answer 1

Along with Swift 4 (Foundation) now it is natively supported in both ways, JSON string to an object - an object to JSON string. Please see Apple's documentation here JSONDecoder() and here JSONEncoder()

JSON String to Object

let jsonData = jsonString.data(using: .utf8)!
let decoder = JSONDecoder()
let myStruct = try! decoder.decode(myStruct.self, from: jsonData)

Swift Object to JSONString

let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted
let data = try! encoder.encode(myStruct)
print(String(data: data, encoding: .utf8)!)

You can find all details and examples here Ultimate Guide to JSON Parsing With Swift 4

Answer 2

Not sure if lib/framework exists, but if you would like to do it automatically and you would like to avoid manual labour :-) stick with MirrorType ...

class U {

  var id: Int
  var name: String

  init(id: Int, name: String) {
    self.id = id
    self.name = name
  }

}

extension U {

  func JSONDictionary() -> Dictionary<String, Any> {
    var dict = Dictionary<String, Any>()

    let mirror = reflect(self)

    var i: Int
    for i = 0 ; i < mirror.count ; i++ {
      let (childName, childMirror) = mirror[i]

      // Just an example how to check type
      if childMirror.valueType is String.Type {
        dict[childName] = childMirror.value
      } else if childMirror.valueType is Int.Type {
        // Convert to NSNumber for example
        dict[childName] = childMirror.value
      }
    }

    return dict
  }

}

Take it as a rough example, lacks proper conversion support, lacks recursion, ... It's just MirrorType demonstration ...

P.S. Here it's done in U, but you're going to enhance NSManagedObject and then you'll be able to convert all NSManagedObject subclasses. No need to implement this in all subclasses/managed objects.

Answer 3

UPDATE: Codable protocol introduced in Swift 4 should be sufficient for most of the JSON parsing cases. Below answer is for people who are stuck in previous versions of Swift and for legacy reasons

EVReflection :

• This works of reflection principle. This takes less code and also supports NSDictionary, NSCoding, Printable, Hashable and Equatable

Example:

    class User: EVObject { # extend EVObject method for the class
       var id: Int = 0
       var name: String = ""
       var friends: [User]? = []
    }

    # use like below
    let json:String = "{\"id\": 24, \"name\": \"Bob Jefferson\", \"friends\": [{\"id\": 29, \"name\": \"Jen Jackson\"}]}"
    let user = User(json: json)

ObjectMapper :

• Another way is by using ObjectMapper. This gives more control but also takes a lot more code.

Example:

    class User: Mappable { # extend Mappable method for the class
       var id: Int?
       var name: String?

       required init?(_ map: Map) {

       }

       func mapping(map: Map) { # write mapping code
          name    <- map["name"]
          id      <- map["id"]
       }

    }

    # use like below
    let json:String = "{\"id\": 24, \"name\": \"Bob Jefferson\", \"friends\": [{\"id\": 29, \"name\": \"Jen Jackson\"}]}"
    let user = Mapper<User>().map(json)