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# AUImplementorValueProvider

A block called to fetch a parameter’s current value from the audio unit implementation.

```
typealias AUImplementorValueProvider = (AUParameter) -> AUValue
```

## Discussion

This block is only of interest to audio unit subclasses.

The block returns the current value of the parameter.

The block takes the following parameters:

- param: The parameter to query.

## See Also

[`implementorValueProvider`](/documentation/AudioToolbox/AUParameterNode/implementorValueProvider)

The callback for refreshing known stale values in a parameter tree.


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