Questions on PostGameplayEffectExecute & ApplyGameplayEffectToTarget

Development Programming & Scripting C++
1

Hi guys,

I am new to UE4, and I am learning the ability system right now, using c++.

I got stuck now, I want to apply a gameplay effect of health damage to the attribute set of the enemy. However, I am unable to do that, I think there is something wrong with my code in either ApplyGameplayEffectToTarget / PostGameplayEffectExecute, but I am really not sure.

Please help me guys!


#include "MeleeAbility.h"
#include "Abilities/Tasks/AbilityTask_PlayMontageAndWait.h"
#include "Abilities/GameplayAbility_Montage.h"
#include "Abilities/Tasks/AbilityTask_WaitGameplayEvent.h"
#include "GameplayTagsManager.h"
#include "AbilitySystemBlueprintLibrary.h"
#include "Enemy.h"

void UMeleeAbility::ActivateAbility(const FGameplayAbilitySpecHandle Handle, const FGameplayAbilityActorInfo* ActorInfo, const FGameplayAbilityActivationInfo ActivationInfo, const FGameplayEventData* TriggerEventData)
{
Super::ActivateAbility(Handle, ActorInfo, ActivationInfo, TriggerEventData);

AbilityHandle = Handle;
AbilityActorInfo = ActorInfo;
AbilityActivationInfo = ActivationInfo;

CommitAbility(Handle, ActorInfo, ActivationInfo);

if (CombatMontage)
{
int32 Skill = FMath::RandRange(0, 2);

switch (Skill)
{
case 0:
SkillSet = "Attack_1";
break;
case 1:
SkillSet = "Attack_2";
break;
case 2:
SkillSet = "Attack_3";
break;
default:
;
}

// Play the combat montage
UAbilityTask_PlayMontageAndWait* MontageProxy = UAbilityTask_PlayMontageAndWait::CreatePlayMontageAndWaitProxy(this, "None", CombatMontage, 1.f, SkillSet);
MontageProxy->Activate();

MontageProxy->OnCompleted.AddDynamic(this, &UMeleeAbility::AbilityFinish);
MontageProxy->OnBlendOut.AddDynamic(this, &UMeleeAbility::AbilityFinish);
MontageProxy->OnInterrupted.AddDynamic(this, &UMeleeAbility::AbilityFinish);
MontageProxy->OnCancelled.AddDynamic(this, &UMeleeAbility::AbilityFinish);
}

// Listen to the specific gameplay event
FGameplayTag DamageTag = UGameplayTagsManager::Get().RequestGameplayTag(TEXT("skill.melee.DealDamage"));

UAbilityTask_WaitGameplayEvent* DamageEvent = UAbilityTask_WaitGameplayEvent::WaitGameplayEvent(this, DamageTag);

DamageEvent->EventReceived.AddDynamic(this, &UMeleeAbility::AbilityDamage);
DamageEvent->Activate();
}

void UMeleeAbility::AbilityDamage(FGameplayEventData Payload)
{
AActor* EnemyTarget = const_cast<AActor*>(Payload.Target);

FGameplayAbilityTargetDataHandle Target = UAbilitySystemBlueprintLibrary::AbilityTargetDataFromActor(EnemyTarget);

if (DamageEffect)
{
ApplyGameplayEffectToTarget(AbilityHandle, AbilityActorInfo, AbilityActivationInfo, Target, DamageEffect, 1.f);
}
}



#include "CharacterBaseAttributeSet.h"
#include "GameplayEffectExtension.h"
#include "GameplayEffectTypes.h"

UCharacterBaseAttributeSet::UCharacterBaseAttributeSet()
:Health(200.f)
{

}

void UCharacterBaseAttributeSet::PostGameplayEffectExecute(const FGameplayEffectModCallbackData& Data)
{
Super::PostGameplayEffectExecute(Data);

if (Data.EvaluatedData.Attribute.GetUProperty() == FindFieldChecked<UProperty>(UCharacterBaseAttributeSet::StaticClass(), GET_MEMBER_NAME_CHECKED(UCharacterBaseAttributeSet, Health)))
{
UE_LOG(LogTemp, Warning, TEXT("My health now is: %f"), Health.GetCurrentValue());
}

UE_LOG(LogTemp, Warning, TEXT("TESTING"));
}
2

It is highly recommended that you view this project:
tranek/GASDocumentation: My understanding of Unreal Engine 4’s GameplayAbilitySystem plugin with a simple multiplayer sample project. (github.com)

3

Were you able to solve this? I’m experiencing similar issues where the attribute manipulation just doesn’t want to happen when using ApplyGameplayEffectToTarget.

4

Solve this by replacing UProperty with FProperty like this:

	auto Property = FindFieldChecked<FProperty>(UAttributeSetBase::StaticClass(),
		GET_MEMBER_NAME_CHECKED(UAttributeSetBase, Health));
	auto Property2 = Data.EvaluatedData.Attribute.GetUProperty();

	if (Property == Property2)
	{
		UE_LOG(LogTemp, Warning, TEXT("Health: %f"), Health.GetCurrentValue());
	}