Replication of properties in a component

Development Programming & Scripting C++
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1

My goal is to replicate hp current value in the following setup:

a UActorComponent named UResourceComponent that contains, among other fields, the following:

UPROPERTY(EditAnywhere,Replicated, BlueprintReadWrite, Category = "Details")
float CurrentValue=100.f;

and by using a tutorial, the following code for replication:

in the header:

virtual void GetLifetimeReplicatedProps(TArray< FLifetimeProperty > & OutLifetimeProps) const override;

virtual bool IsSupportedForNetworking() const override
{
	return true;
}

and the cpp:

void UResourceComponent::GetLifetimeReplicatedProps(TArray<FLifetimeProperty>& OutLifetimeProps) const
{
	Super::GetLifetimeReplicatedProps(OutLifetimeProps);

	DOREPLIFETIME(UResourceComponent, CurrentValue);
}

next up, is another UActorComponent named UVitalsComponent
this component holds 3 UResourceComponent as resource bars. for now i am trying to replicate only the hp bar

the header:

UPROPERTY(EditAnywhere,Replicated, BlueprintReadWrite, Category = "Initialization", meta = (EditCondition = bUseResourceHP))
	UResourceComponent* BarHP;	

virtual bool ReplicateSubobjects(class UActorChannel *Channel, class FOutBunch *Bunch, FReplicationFlags *RepFlags) override;


virtual void GetLifetimeReplicatedProps(TArray< FLifetimeProperty > & OutLifetimeProps) const override;

virtual bool IsSupportedForNetworking() const override
{
	return true;
}

and again, following a tutorial, the cpp:
setting BarHP->SetIsReplicated(true); in the constructor

bool UVitalsComponent::ReplicateSubobjects(class UActorChannel *Channel, class FOutBunch *Bunch, FReplicationFlags *RepFlags)
{
	bool WroteSomething = Super::ReplicateSubobjects(Channel, Bunch, RepFlags);

	if (BarHP != nullptr)
	{
		WroteSomething |= Channel->ReplicateSubobject(BarHP, *Bunch, *RepFlags);
	}

	return WroteSomething;
}
void UVitalsComponent::GetLifetimeReplicatedProps(TArray< FLifetimeProperty > & OutLifetimeProps) const
{
	Super::GetLifetimeReplicatedProps(OutLifetimeProps);

	DOREPLIFETIME(UVitalsComponent, BarHP);
}

lastly, a character class named Acpp_BaseGameCharacter.
in blueprint i create a class derived from VitalsComponent and add it to the character. after failed tests i decided to search and save the component in the BeginPlay method.

Header:

virtual bool ReplicateSubobjects(class UActorChannel *Channel, class FOutBunch *Bunch, FReplicationFlags *RepFlags) override;

virtual void GetLifetimeReplicatedProps(TArray< FLifetimeProperty > & OutLifetimeProps) const override;
 
 UPROPERTY(VisibleAnywhere,Replicated)
class UVitalsComponent* vitalsComponent;

and the cpp:

void Acpp_BaseGameCharacter::GetLifetimeReplicatedProps(TArray<FLifetimeProperty>& OutLifetimeProps) const
{
	Super::GetLifetimeReplicatedProps(OutLifetimeProps);

	DOREPLIFETIME(Acpp_BaseGameCharacter, vitalsComponent);
}

bool Acpp_BaseGameCharacter::ReplicateSubobjects(class UActorChannel *Channel, class FOutBunch *Bunch, FReplicationFlags *RepFlags)
{
	bool WroteSomething = Super::ReplicateSubobjects(Channel, Bunch, RepFlags);

	if (vitalsComponent != nullptr)
	{
		WroteSomething |= Channel->ReplicateSubobject(vitalsComponent, *Bunch, *RepFlags);
	}

	return WroteSomething;
}


void Acpp_BaseGameCharacter::BeginPlay()
{
	Super::BeginPlay();
	vitalsComponent = FindComponentByClass<UVitalsComponent>();
	vitalsComponent->SetIsReplicated(true);
}

i expect that whenever i change the value of current hp on the server, the clients will get updated. it doesnt work and i feel really stupid and sure that i missed something.

2

Hello.

I’d start with moving following line to the constructor of your Acpp_BaseGameCharacter. I’m guessing it might be way to late (world initialization wise) to set that in BeginPlay.

vitalsComponent->SetIsReplicated(true);

Edit:

Also, make sure your component contructor contains this:

bReplicates = true;

If that doesn’t fix it, I’d remove your ReplicateSubobjects implementation. To be honest i never had to use that to properly replicate component properties. Maybe it’s messing up default replication somehow.

3

thank you for the reply
vitalsComponent is created in the blueprint, hence im not sure if it will be found at the construct time.
moreover, in the blueprint i also set the replication flag to true.
i added ReplicateSubobjects method only after i tried to make it work without it.

4

Ah, I see. Then yeah, you won’t find it in contructor. :confused:

5

I’ve edited my answer (added part about bReplicates property). You might be missing this.

6

You could also try to do it in AActor::PostInitializeComponents. It’s called somewhere during blueprint compilation/creation/opening. Add some log to make sure so you’ll know when it executes.

7

thank you i will try the AActor::PostInitializeComponents.
as for breplicates - yeah, same same :stuck_out_tongue: