 	case startTime
 	case endTime
 	case date
-	case newParticipant
+	case addParticipant
+	case expectedDuration
+	case currentTopic
+	case addTopic
 	
 	// TODO: assign callbacks to the enum values?
 }

		update(operation: UpdateOperation.title, attribute: "title", value: title as CKRecordValue, meeting: meeting)
	}
	
	func update(newParticipant: User, meeting: Meeting) {
		let userRecordID = CKRecordID(recordName: newParticipant.ID)
		let userReference = CKReference(recordID: userRecordID, action: .none)
		
		update(operation: .newParticipant, attribute: "", value: userReference, meeting: meeting)
	}
	
	
	

			if let record = record {
				
				switch operation {
				case .title, .startTime, .endTime, .date, .expectedDuration, .currentTopic:
					self.assign(attribute: attribute, value: value, record: record)
				case .addParticipant:
					self.assign(addParticipant: value, record: record)
				case .addTopic:
					self.assign(addTopic: value, record: record)
				default:
					print("Update operation not found.") // TODO: define error
				}
