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# ar_session_data_provider_state_change_handler_t

A handler that the session calls when one or more data providers associated with it change state.

```
typedef void (^)(NSObject<OS_ar_data_providers> *, ar_data_provider_state_t, NSObject<OS_ar_error> *, NSObject<OS_ar_data_provider> *) ar_session_data_provider_state_change_handler_t;
```

## Parameters

`data_providers`

The collection of data providers that changed state.

`new_state`

The data provider state that triggered the event.

`error`

An error associated with the state change, if any. Also see `ar_session_error_code_t`.

`failed_data_provider`

The data provider that failed and caused the error, if any.

---

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