In this lesson, you will learn how to make your custom Actor Components "network-aware" so they can synchronize data and execute logic across all connected clients.
Moving Beyond Actors
Until now, we’ve focused on replicating AActor classes. However, modular design often pushes logic into UActorComponent classes (like a HealthComponent or InventoryComponent). Components do not replicate by default; they depend on their owner's replication settings. To make them sync data, we must explicitly enable replication within the component and implement a GetLifetimeReplicatedProps override, just as we do for Actors.
Syncing Properties via Replication
When you want a component property to stay in sync—such as the current "Shield Strength"—you define the variable with the UPROPERTY(Replicated) macro. Inside your component’s .cpp file, you map these to the DOREPLIFETIME macro.
void UMyComponent::GetLifetimeReplicatedProps(TArray<FLifetimeProperty>& OutLifetimeProps) const {
Super::GetLifetimeReplicatedProps(OutLifetimeProps);
DOREPLIFETIME(UMyComponent, ShieldStrength);
}
This tells the server to push the value of ShieldStrength to every client whenever it changes. Without this, the client would only see the default value initialized at spawn.
Protecting Logic with Server-Side RPCs
Replication handles the state, but RPCs handle the action. If a player triggers an ability defined in a component, that logic must happen on the server to prevent cheating. You should always mark these functions as Server and include WithValidation in the UFUNCTION macro.
The _Validate function is your security checkpoint. If a client tries to trigger a "Heal" RPC but their character is already dead, the validation function returns false, effectively dropping the packet and logging the unauthorized attempt. By combining Replicated properties for state display and Server RPCs for gameplay logic, you create a robust, secure bridge between your component and the network.
Key Takeaway: To replicate components, you must enable IsReplicatedByDefault, define properties in GetLifetimeReplicatedProps, and always validate your Server RPCs to ensure gameplay integrity.