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# restartPolling()

Restarts the polling sequence so the reader session can discover new tags.

```
func restartPolling()
```

## Discussion

After restarting the polling sequence, the reader session sends newly detected tags to the session’s delegate method [`readerSession(_:didDetect:)`](/documentation/CoreNFC/NFCNDEFReaderSessionDelegate/readerSession(_:didDetect:)).

> Note:
> Tags detected before polling restarts are invalid. Your app should discard any references it has to the invalid tags to free system resources.

Calling [`restartPolling()`](/documentation/CoreNFC/NFCNDEFReaderSession/restartPolling()) has no effect when:

- The session is invalid. If you need to restart the reader session, create a new [`NFCNDEFReaderSession`](/documentation/CoreNFC/NFCNDEFReaderSession).
- The session’s delegate doesn’t implement the [`readerSession(_:didDetect:)`](/documentation/CoreNFC/NFCNDEFReaderSessionDelegate/readerSession(_:didDetect:)) method. When this method is missing, the session calls [`readerSession(_:didDetectNDEFs:)`](/documentation/CoreNFC/NFCNDEFReaderSessionDelegate/readerSession(_:didDetectNDEFs:)) to inform the delegate of new NDEF messages, then restarts the polling sequence.

---

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