I have two classes: Board and Formation. There is a relationship between them - each Formation is assigned a single Board. Multiple formations can be assigned to a board. This relationship is set up in CoreData as well. I am having trouble using Core Data with Codable to encode that relationship. It throws a bad access error. I have done my research online, but most of the articles do not touch on relationships. Please advise. public class Board: NSManagedObject, Codable {   enum CodingKeys: CodingKey {     case lastEdited, name, notes, song, uniqueId, subFormations   }     required convenience public init(from decoder: Decoder) throws {         guard let context = decoder.userInfo[CodingUserInfoKey.managedObjectContext] as? NSManagedObjectContext else {           throw DecoderConfigurationError.missingManagedObjectContext         }         self.init(context: context)         let container = try decoder.container(keyedBy: CodingKeys.self)         do{         self.lastEdited = try container.decode(Date.self, forKey: .lastEdited)         self.name = try container.decode(String?.self, forKey: .name)         self.notes = try container.decode(String?.self, forKey: .notes)         self.song = try container.decode(String?.self, forKey: .song)         self.uniqueId = try container.decode(String.self, forKey: .uniqueId)             self.subFormations = try container.decode(Set<Formation>.self, forKey: .subFormations)         }   catch{             print("Error Decoding Board")         } }      public func encode(to encoder: Encoder) throws {         var container = encoder.container(keyedBy: CodingKeys.self)         try container.encode(lastEdited, forKey: .lastEdited)         try container.encode(name, forKey: .name)         try container.encode(notes, forKey: .notes)        try container.encode(song, forKey: .song)         try container.encode(uniqueId, forKey: .uniqueId)         try container.encode(subFormations, forKey: .subFormations)       } public class Formation: NSManagedObject, Codable {   enum CodingKeys: CodingKey {     case name, position, songTime, uniqueId, waitTime, dancers, formationOwner   }   required convenience init(from decoder: Decoder) throws {     guard let context = decoder.userInfo[CodingUserInfoKey.managedObjectContext] as? NSManagedObjectContext else {       throw DecoderConfigurationError.missingManagedObjectContext     }     self.init(context: context)     let container = try decoder.container(keyedBy: CodingKeys.self)     self.name = try container.decode(String.self, forKey: .name)     self.position = try container.decode(Int16.self, forKey: .position)     self.songTime = try container.decode(Float.self, forKey: .songTime)     self.uniqueId = try container.decode(String.self, forKey: .uniqueId)     self.waitTime = try container.decode(Int16.self, forKey: .waitTime)     self.formationOwner = try container.decode(Board.self, forKey: .formationOwner)   }     public func encode(to encoder: Encoder) throws {         var container = encoder.container(keyedBy: CodingKeys.self)         try container.encode(name, forKey: .name)         try container.encode(position, forKey: .position)         try container.encode(songTime, forKey: .songTime)        try container.encode(uniqueId, forKey: .uniqueId)         try container.encode(waitTime, forKey: .waitTime)         try container.encode(formationOwner as Board, forKey: .formationOwner)       } //Formation Properties     @NSManaged public var name: String?     @NSManaged public var position: Int16     @NSManaged public var songTime: Float     @NSManaged public var uniqueId: String     @NSManaged public var waitTime: Int16     @NSManaged public var dancers: NSSet?     @NSManaged public var formationOwner: Board //Board Properties  try container.encode(lastEdited, forKey: .lastEdited)         try container.encode(name, forKey: .name)         try container.encode(notes, forKey: .notes)        try container.encode(song, forKey: .song)         try container.encode(uniqueId, forKey: .uniqueId)         try container.encode(subFormations, forKey: .subFormations) //Thread 1: EXC_BAD_ACCESS