The GameplayAbilities API allows you to associate a set of attributes, that is, UAttributeSet, to an Actor. UAttributeSet describes properties appropriate for that Actor's in-game attributes, such as Hp, Mana, Speed, Armor, AttackDamage, and so on. You can either define a single game-wide set of attributes common to all Actors, or several different sets of attributes appropriate for the different classes of actors.
AbilitySystemComponent is the first thing you will need to add to your actors to equip them to use GameAbilities API and UAttributeSets. To define your custom UAttributeSet, you will simply derive from the UAttributeSet base class and extend the base class with your own series of UPROPERTY members. After that, you must register your custom AttributeSet with your Actor class' AbilitySystemComponent.
- Link to the
GameplayAbilitiesAPI in yourProjectName.Build.csfile. - In its own file, derive from the
UAttributeSetclass and deck the class out with a set ofUPROPERTYthat you want each Actor to have in their property set. For example, you might want to declare yourUAttributeSetderivate class similar to the following piece of code:#include "Runtime/GameplayAbilities/Public/AttributeSet.h" #include "GameUnitAttributeSet.generated.h" UCLASS(Blueprintable, BlueprintType) class CHAPTER12_API UGameUnitAttributeSet : public UAttributeSet { GENERATED_BODY() public: UGameUnitAttributeSet( const FObjectInitializer& PCIP ); UPROPERTY( EditAnywhere, BlueprintReadWrite, Category = GameUnitAttributes ) float Hp; UPROPERTY( EditAnywhere, BlueprintReadWrite, Category = GameUnitAttributes ) float Mana; UPROPERTY( EditAnywhere, BlueprintReadWrite, Category = GameUnitAttributes ) float Speed; }; - Connect
GameUnitAttributeSetwith yourAbilitySystemComponentinside yourActorclass by calling the following code:AbilitySystemComponent->InitStats( UGameUnitAttributeSet::StaticClass(), NULL );
You can put this call somewhere in
PostInitializeComponents(), or in code that is called later than that. - Once you have registered
UAttributeSet, you can move on with the next recipe and applyGameplayEffectto some of the elements in the attribute set. - Be sure your
Actorclass object implementsIAbilitySystemInterfaceby deriving from it. This is extremely important as theUAbilitySetobject will attempt a cast toIAbilitySystemInterfaceto callGetAbilitySystemComponent()on it at various places in the code.
UAttributeSets simply allow you to enumerate and define attributes of different actors. GameplayEffects will be your means to make changes to the attributes of a specific actor.
You can code in definitions of GameplayEffects, which will be things that act on the AbilitySystemComponent's AttributeSet collections. You can also write GameplayTasks for generic functions that run at specific time or events, or even in response to tag addition (GameplayTagResponseTable.cpp). You can define GameplayTags to modify GameplayAbility behavior as well as select and match gameplay units during play.