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# CTTelephonyNetworkInfoDelegate

The methods that the system invokes when data service changes occur.

```
protocol CTTelephonyNetworkInfoDelegate : NSObjectProtocol
```

## Topics

### Responding to Data Service Changes

[`-  dataServiceIdentifierDidChange:`](/documentation/CoreTelephony/CTTelephonyNetworkInfoDelegate/dataServiceIdentifierDidChange(_:))

Informs the delegate when the identifier changes for the service that’s currently providing data.

## Relationships

### Inherits From

[`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol)

---

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