FSigHandle

FSigHandle

RAII ownership of listener registrations. Destroying it unregisters everything registered through it.

Declared in Plugins/GMP/Source/GMP/GMP/GMPSignals.inl:89

// auto disconnect signals
class FSigHandle : public FSigCollection
{
public:
    ~FSigHandle() { DisconnectAll(); }
};

Aliased as FGMPSignalsHandle in GMP/Shared/GMPCore.h:45.

What problem it solves

A listener outliving its owner is a dangling call. For UObject owners GMP can check weak-pointer staleness, but a plain C++ class has nothing to check — so it needs an owner object whose destructor does the unregistering. That object is FSigHandle.

class FMyThing            // not a UObject
{
    GMP::FSigHandle Handle;
public:
    FMyThing()
    {
        FGMPHelper::ListenMessage(MSGKEY("Common.Action"), &Handle,
            [this](Type1& P1){ /* ... */ });
    }
    // ~FMyThing destroys Handle, which disconnects the listener
};

GMPSignalsInc.h:28 declares a GMPSignalHandle member for classes that want this by convention rather than by hand.

Behaviour

• Disconnects all, not one. It is a collection (FSigCollection); every registration made against it goes away together.
• Order is not guaranteed across registrations, and should not be relied on.
• Destroying the handle is the only thing that has to happen. There is no explicit teardown call to forget.
• A handle is not copyable in a meaningful sense — it owns registrations, so treat it as a member, not a value to pass around.

When you do not need it

• The owner is a UObject — pass the object itself; staleness is checked on dispatch.
• The owner is shared-pointer managed — CreateSPLambda covers it.
• You want to unregister one specific listener rather than all of them — keep the FGMPKey returned by the listen call and unlisten with that.

Common mistake

Registering with this from a non-UObject class and expecting it to be safe. It is not; there is nothing for GMP to check. Either hold an FSigHandle or manage the FGMPKey yourself.

See also

ListenMessage family · FGMPKey · FSigSource