[#BloombergLP-balb-ControlManager-registerDefaultHandler]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/balb.adoc[balb]::xref:BloombergLP/balb/ControlManager.adoc[ControlManager]::registerDefaultHandler
:relfileprefix: ../../../
:mrdocs:

Register a handler for messages with unregistered prefixes.

== Synopsis

Declared in `<balb_controlmanager.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
registerDefaultHandler(xref:BloombergLP/balb/ControlManager/ControlHandler.adoc[ControlHandler] const& hander);
----

== Description

Register the specified `handler` to be invoked whenever a control message having an unregistered (case‐insensitive) `prefix` is received by this control manager. Return a positive value if an existing callback was replaced, return 0 if no replacement occurred, and return a negative value otherwise.

== Return Value

positive if replaced, 0 if new, negative otherwise

== Parameters

[cols="1,4"]
|===
| Name| Description
| *hander*
| callback invoked for messages with unregistered prefixes
|===


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