# getCallback method | |
Function getCallback | |
(int txid) | |
<p>Returns the callback associated with the given response message.</p> | |
<p>Used by subclasses of <a href="../../package-fidl_fidl/Proxy-class.md">Proxy<T></a> to retrieve registered callbacks when | |
handling response messages.</p> | |
## Implementation | |
```dart | |
Function? getCallback(int txid) { | |
final Function? result = _callbackMap.remove(txid); | |
if (result == null) { | |
proxyError('Message had unknown request id: $txid'); | |
return null; | |
} | |
return result; | |
} | |
``` | |