<!--
{
  "availability" : [
    "iOS: 17.4.0 -",
    "iPadOS: 17.4.0 -",
    "macCatalyst: -"
  ],
  "documentType" : "symbol",
  "framework" : "CoreNFC",
  "identifier" : "/documentation/CoreNFC/CardSession/Event",
  "metadataVersion" : "0.1.0",
  "role" : "Enumeration",
  "symbol" : {
    "kind" : "Enumeration",
    "modules" : [
      "Core NFC"
    ],
    "preciseIdentifier" : "s:7CoreNFC11CardSessionC5EventO"
  },
  "title" : "CardSession.Event"
}
-->

# CardSession.Event

A type that enumerates events produced by a card session.

```
enum Event
```

## Topics

### Events

[`case sessionStarted`](/documentation/CoreNFC/CardSession/Event/sessionStarted)

The card session successfully started.

[`case readerDetected`](/documentation/CoreNFC/CardSession/Event/readerDetected)

The session detected the RF field of an external NFC reader.

[`case received(CardSession.APDU)`](/documentation/CoreNFC/CardSession/Event/received(_:))

The session received an Application Programming Data Unit (ADPU).

[`class APDU`](/documentation/CoreNFC/CardSession/APDU)

An Application Programming Data Unit (APDU) received from the NFC card reader.

[`case readerDeselected`](/documentation/CoreNFC/CardSession/Event/readerDeselected)

The session lost the RF link or the currently-selected Application Identifier (AID) became deselected.

[`case sessionInvalidated(reason: CardSession.Error)`](/documentation/CoreNFC/CardSession/Event/sessionInvalidated(reason:))

The session became invalid.

## Relationships

### Conforms To

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

[`Sendable`](/documentation/Swift/Sendable)

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)