Example for calling a blueprint event / function from c++ in unreal engine 4.

ue4-call-blueprint.cpp

// This example shows how to call a blueprint event / function from c++ in unreal engine 4.
// In this example we call a blueprint event named "ServerRequestPossess" (see below).

// The current character for instance.
// This character must be implemented in blueprint and provides the blueprint event named "ServerRequestPossess".
ACharacter* CurrentCharacter = <instance of ACharacter>;

// Just an another character. It could by any object.
ACharacter* AnotherCharacter = Cast<class ACharacter>(Hit.Actor);

if (AnotherCharacter == nullptr)
{
    return;
}

// ServerRequestPossess is a blueprint implemented event.
// The event has one input parameter of type "Character".
UFunction* Function = CurrentCharacter->GetClass()->FindFunctionByName(FName("ServerRequestPossess"));

if (Function == nullptr)
{
    return;
}

// Parameters of the event.
// In this case the structure contains only the one input parameter of type "Character" as mentioned above.
struct FLocalParameters
{
    class ACharacter* PlayerCharacter;
};

FLocalParameters Parameters;
Parameters.PlayerCharacter = AnotherCharacter;

CurrentCharacter->ProcessEvent(Function, &Parameters);

Thanks