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# AudioObjectPropertyListenerBlock

```
typealias AudioObjectPropertyListenerBlock = (UInt32, UnsafePointer<AudioObjectPropertyAddress>) -> Void
```

## Parameters

`inNumberAddresses`

The number of elements in the inAddresses array.

`inAddresses`

An array of AudioObjectPropertyAddresses indicating which properties
changed.

## Discussion

\abstract Clients register an AudioObjectPropertyListenerBlock with an AudioObject in
order to receive notifications when the properties of the object change.
\discussion Listeners will be called when possibly many properties have changed.
Consequently, the implementation of a listener must go through the array of
addresses to see what exactly has changed. Note that the array of addresses will
always have at least one address in it for which the listener is signed up to
receive notifications about but may contain addresses for properties for which
the listener is not signed up to receive notifications.

---

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