Thread 1: signal SIGABRT

import UIKit

class User: NSObject {

    @objc var name: String?
    @objc var code: String?
    @objc var accountType: String?
    var timestamp: TimeInterval?

}

ref = Database.database().reference().child("users")

        let key = ref?.childByAutoId().key

        let date = Date()
        let timestamp = date.timeIntervalSince1970

        let dataSaved : [String:Any] = ["name":nameTxt.text! as String, "code":codeTxt.text! as String, "accountType":accountType as String,"timestamp":timestamp as TimeInterval]
        ref?.child(key!).setValue(dataSaved)

@objc func fetchUsers(){

        // snapshot

        handle = ref?.child("users").observe(.childAdded, with: { (snapshot) in
            if let dictionary = snapshot.value as? [String : AnyObject]{

                print(dictionary)

                let user = User()
                user.setValuesForKeys(dictionary)
                self.myList.append(user)


                DispatchQueue.main.async {
                    self.myTableview.reloadData()
                }

            }
        })



    }

2018-01-21 19:44:19.741130+0300 AddMe Social[14827:522721] [MC] Lazy loading NSBundle MobileCoreServices.framework
2018-01-21 19:44:19.743342+0300 AddMe Social[14827:522721] [MC] Loaded MobileCoreServices.framework
2018-01-21 19:44:19.753564+0300 AddMe Social[14827:522721] [MC] System group container for systemgroup.com.apple.configurationprofiles path is /Users/Maher/Library/Developer/CoreSimulator/Devices/144580E8-06C1-490F-BD08-CBA0F1994EBB/data/Containers/Shared/SystemGroup/systemgroup.com.apple.configurationprofiles
2018-01-21 19:44:19.799641+0300 AddMe Social[14827:522957] [Firebase/Analytics][I-ACS023007] Firebase Analytics v.40002000 started
2018-01-21 19:44:19.800 AddMe Social[14827] <Notice> [Firebase/Analytics][I-ACS023007] Firebase Analytics v.40002000 started
2018-01-21 19:44:19.801215+0300 AddMe Social[14827:522957] [Firebase/Analytics][I-ACS023008] To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled ()
2018-01-21 19:44:19.808 AddMe Social[14827] <Notice> [Firebase/Analytics][I-ACS023008] To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled ()
2018-01-21 19:44:19.920472+0300 AddMe Social[14827:522721] [MC] Reading from private effective user settings.
2018-01-21 19:44:19.926419+0300 AddMe Social[14827:522976] Could not successfully update network info during initialization.
2018-01-21 19:44:20.067907+0300 AddMe Social[14827:522966] [BoringSSL] Function boringssl_context_get_peer_sct_list: line 1754 received sct extension length is less than sct data length
2018-01-21 19:44:20.188815+0300 AddMe Social[14827:522957] [Firebase/Analytics][I-ACS003007] Successfully created Firebase Analytics App Delegate Proxy automatically. To disable the proxy, set the flag FirebaseAppDelegateProxyEnabled to NO in the Info.plist
2018-01-21 19:44:20.190 AddMe Social[14827] <Notice> [Firebase/Analytics][I-ACS003007] Successfully created Firebase Analytics App Delegate Proxy automatically. To disable the proxy, set the flag FirebaseAppDelegateProxyEnabled to NO in the Info.plist
2018-01-21 19:44:20.514132+0300 AddMe Social[14827:522957] [Firebase/Analytics][I-ACS032003] iAd framework is not linked. Search Ad Attribution Reporter is disabled.
2018-01-21 19:44:20.514 AddMe Social[14827] <Warning> [Firebase/Analytics][I-ACS032003] iAd framework is not linked. Search Ad Attribution Reporter is disabled.
2018-01-21 19:44:20.517536+0300 AddMe Social[14827:522976] [Firebase/Analytics][I-ACS023012] Firebase Analytics enabled
2018-01-21 19:44:20.517 AddMe Social[14827] <Notice> [Firebase/Analytics][I-ACS023012] Firebase Analytics enabled
2018-01-21 19:44:20.523193+0300 AddMe Social[14827:522954] TIC Read Status [1:0x0]: 1:57
2018-01-21 19:44:20.523372+0300 AddMe Social[14827:522954] TIC Read Status [1:0x0]: 1:57
["name": fdgf, "timestamp": 1516545687.582723, "code": dfgd, "accountType": Twitter]
2018-01-21 19:44:23.041444+0300 AddMe Social[14827:522721] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<AddMe_Social.User 0x6040000e7780> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key timestamp.'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000010c8511cb __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000010ad90f41 objc_exception_throw + 48
    2   CoreFoundation                      0x000000010c851119 -[NSException raise] + 9
    3   Foundation                          0x000000010a7b31e3 -[NSObject(NSKeyValueCoding) setValue:forKey:] + 292
    4   Foundation                          0x000000010a811ed2 -[NSObject(NSKeyValueCoding) setValuesForKeysWithDictionary:] + 283
    5   AddMe Social                        0x00000001091514ed _T012AddMe_Social10MainScreenC10fetchUsersyyFySo12DataSnapshotCcfU_ + 1037
    6   AddMe Social                        0x000000010915181a _T012AddMe_Social10MainScreenC10fetchUsersyyFySo12DataSnapshotCcfU_TA + 58
    7   AddMe Social                        0x000000010915191e _T0So12DataSnapshotCIxx_ABIyBy_TR + 62
    8   AddMe Social                        0x00000001091ddad9 __63-[FIRDatabaseQuery observeEventType:withBlock:withCancelBlock:]_block_invoke + 37
    9   AddMe Social                        0x000000010920a7fd __43-[FChildEventRegistration fireEvent:queue:]_block_invoke.55 + 88
    10  libdispatch.dylib                   0x00000001114ef3f7 _dispatch_call_block_and_release + 12
    11  libdispatch.dylib                   0x00000001114f043c _dispatch_client_callout + 8
    12  libdispatch.dylib                   0x00000001114fb6f0 _dispatch_main_queue_callback_4CF + 628
    13  CoreFoundation                      0x000000010c813ef9 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
    14  CoreFoundation                      0x000000010c7d8662 __CFRunLoopRun + 2402
    15  CoreFoundation                      0x000000010c7d7a89 CFRunLoopRunSpecific + 409
    16  GraphicsServices                    0x0000000113b3f9c6 GSEventRunModal + 62
    17  UIKit                               0x000000010e73f23c UIApplicationMain + 159
    18  AddMe Social                        0x000000010915dd77 main + 55
    19  libdyld.dylib                       0x000000011156cd81 start + 1
    20  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)