In this lesson, you will learn how to create flexible C++ functions that provide a default behavior while granting Blueprint designers the power to override or extend them.
Why use Blueprint Native Events?
Sometimes, you want a function to perform a standard action (like playing a sound or applying damage), but you also want artists or designers to be able to add custom logic in Blueprints without completely replacing your C++ work. The BlueprintNativeEvent specifier is the bridge that makes this possible.
The Implementation Pattern
To create one, you add the BlueprintNativeEvent keyword to your UFUNCTION macro in your header file.
Crucially, when you implement this in your C++ source file, you do not name the function the same as in the header. Instead, you append _Implementation to the name. Unreal’s build system automatically calls this C++ version if no Blueprint override exists, or if the Blueprint logic specifically calls the "Parent" function.
// Header File
UFUNCTION(BlueprintNativeEvent, Category = "Gameplay")
void OnInteraction();
// Source File
void AMyActor::OnInteraction_Implementation()
{
// This is the default C++ behavior
UE_LOG(LogTemp, Warning, TEXT("Default interaction occurred!"));
}
How it works for designers
When a designer creates a Blueprint based on your class, they will see OnInteraction in their "Functions" list. By right-clicking it and selecting "Add Event," they can create a graph.
If they add logic to that graph, it runs instead of your C++ code. However, they can right-click the node in their Blueprint graph and select "Add call to parent function." This creates a special node that executes your _Implementation code, allowing the Blueprint to augment your C++ logic rather than just deleting it.
This is the perfect way to maintain strict performance-critical code in C++ while keeping your project accessible for high-level gameplay tuning.
Key Takeaway: Use BlueprintNativeEvent to define a base C++ behavior that Blueprints can override or extend by calling the parent implementation.