13. UE5 RPG限制Attribute的值的范围以及生成结构体

前面几章，我们实现了通过GameplayEffect对Attribute值的修改，比如血量和蓝量，我们都是有一个最大血量和最大蓝量去限制它的最大值，而且血量和蓝量最小值不会小于零。之前我们是没有实现相关限制的，接下来，我们需要在AttributeSet函数里面实现一下对实际值的范围限制。

实现

首先覆盖父类函数，在PreAttributeChange()函数，这个函数会在AttributeSet里的监听的值发生改变前触发回调

virtual void PreAttributeChange(const FGameplayAttribute& Attribute, float& NewValue) override;

回调有返回两个参数，一个是Attribute，我们可以通过此值判断哪个属性被修改掉了，另一个是将要修改成的值，接下来，我们打印一下值，看一下结果。

	if(Attribute == GetHealthAttribute()){UE_LOG(LogTemp, Warning, TEXT("Health: %f"), NewValue);}if(Attribute == GetMaxHealthAttribute()){UE_LOG(LogTemp, Warning, TEXT("MaxHealth: %f"), NewValue);}if(Attribute == GetManaAttribute()){UE_LOG(LogTemp, Warning, TEXT("Mana: %f"), NewValue);}if(Attribute == GetMaxManaAttribute()){UE_LOG(LogTemp, Warning, TEXT("MaxMana: %f"), NewValue);}

编译打开UE，点击场景左下角的输出日志
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选择停靠在布局中

然后让角色去吃药瓶，水晶，以及去踩火堆，看看属性变化，我们会发现所有属性变化，都能够如实的反应在打印上面

接着使用clamp函数将血量和蓝量数值限制在0到最大血量和蓝量的范围内

NewValue = FMath::Clamp(NewValue, 0.f, GetMaxHealth());

运行UE，再查看，发现数值都被限制在了范围内
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PostGameplayEffectExecute

PostGameplayEffectExecute()函数是在数值变化后触发的，一般只会在Instant类型的GameplayEffect才可以触发（Duration和Infinite类的GameplayEffect如果设置Period也可以触发）。
这个函数的应用场景很多，我们可以做一些逻辑操作，比如死亡，无敌不扣血等等。
使用它我们需要先覆盖父类

virtual void PostGameplayEffectExecute(const FGameplayEffectModCallbackData& Data) override;

它只有一个返回参数就是Data，但是Data里面包含的内容很多

	if(Data.EvaluatedData.Attribute == GetHealthAttribute()){UE_LOG(LogTemp, Warning, TEXT("Health: %f"), GetHealth());UE_LOG(LogTemp, Warning, TEXT("Magnitude: %f"), Data.EvaluatedData.Magnitude);}

打开UE可以查看到，当前的血量，以及这次Effect造成的伤害数值。
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我们打一个断点

可以看到Data里面有三项数据

EffectSpec就是效果的实例里面包含很多的数据，我们可以通过它获取到时哪个Actor将此GE应用到目标身上的
EvaluatedData就是修改的数据相关的内容，当前值，修改了多少值，修改的什么属性等等
Target就是目标的ASC
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接下来，我们将从Data中获取到需要的然后封装成一个结构体，方便后续使用。

首先创建一个FEffectProperties的结构体，用于存储施放GE的相关对象和目标的相关对象。这个结构体，将GE的上下文，并将施放者和目标的ASC AvatarActor Controller Character都保存了下来

USTRUCT()
struct FEffectProperties
{GENERATED_BODY()FEffectProperties(){}FGameplayEffectContextHandle EffectContextHandle;UPROPERTY()UAbilitySystemComponent* SourceASC = nullptr;UPROPERTY()AActor* SourceAvatarActor = nullptr;UPROPERTY()AController* SourceController = nullptr;UPROPERTY()ACharacter* SourceCharacter = nullptr;UPROPERTY()UAbilitySystemComponent* TargetASC = nullptr;UPROPERTY()AActor* TargetAvatarActor = nullptr;UPROPERTY()AController* TargetController = nullptr;UPROPERTY()ACharacter* TargetCharacter = nullptr;
};

接下来，创建一个私有函数，我们在这个函数里面去处理生成结构体属性的值。函数接收两个值，一个是PostGameplayEffectExecute()函数返回的Data，另一个是需要填充的结构体。

static void SetEffectProperties(const FGameplayEffectModCallbackData& Data, FEffectProperties& Props);

接着，实现函数，在函数内设置属性，前面将了，可以通过Data获取到相关的属性

void UAttributeSetBase::SetEffectProperties(const FGameplayEffectModCallbackData& Data, FEffectProperties& Props)
{//Source 效果的所有者   Target 效果应用的目标Props.EffectContextHandle = Data.EffectSpec.GetContext();Props.SourceASC = Props.EffectContextHandle.GetOriginalInstigatorAbilitySystemComponent(); //获取效果所有者的ASC//获取效果所有者的相关对象if(IsValid(Props.SourceASC) && Props.SourceASC->AbilityActorInfo.IsValid() && Props.SourceASC->AbilityActorInfo->AvatarActor.IsValid()){Props.SourceAvatarActor = Props.SourceASC->AbilityActorInfo->AvatarActor.Get(); //获取ActorProps.SourceController = Props.SourceASC->AbilityActorInfo->PlayerController.Get(); //获取PlayerControllerif(Props.SourceController == nullptr && Props.SourceAvatarActor != nullptr){if(const APawn* Pawn = Cast<APawn>(Props.SourceAvatarActor)){Props.SourceController = Pawn->GetController();}}if(Props.SourceController){Props.SourceCharacter = Cast<ACharacter>(Props.SourceController->GetPawn());}}if(Data.Target.AbilityActorInfo.IsValid() && Data.Target.AbilityActorInfo->AvatarActor.IsValid()){Props.TargetAvatarActor = Data.Target.AbilityActorInfo->AvatarActor.Get();Props.TargetController = Data.Target.AbilityActorInfo->PlayerController.Get();Props.TargetCharacter = Cast<ACharacter>(Props.TargetAvatarActor);Props.TargetASC = UAbilitySystemBlueprintLibrary::GetAbilitySystemComponent(Props.TargetAvatarActor);}
}

接着，只需要在PostGameplayEffectExecute()内创建一个结构体，并调用函数生成内容即可。

void UAttributeSetBase::PostGameplayEffectExecute(const FGameplayEffectModCallbackData& Data)
{Super::PostGameplayEffectExecute(Data);FEffectProperties Props;SetEffectProperties(Data, Props);}

在使用时，我们就可以通过结构体去获取相应的内容，逻辑更加整洁
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源代码

AttributeSetBase.h

// 版权归暮志未晚所有。#pragma once#include "CoreMinimal.h"
#include "AttributeSet.h"
#include "AbilitySystemComponent.h"
#include "AttributeSetBase.generated.h"// Uses macros from AttributeSet.h
#define ATTRIBUTE_ACCESSORS(ClassName, PropertyName) \
GAMEPLAYATTRIBUTE_PROPERTY_GETTER(ClassName, PropertyName) \
GAMEPLAYATTRIBUTE_VALUE_GETTER(PropertyName) \
GAMEPLAYATTRIBUTE_VALUE_SETTER(PropertyName) \
GAMEPLAYATTRIBUTE_VALUE_INITTER(PropertyName)USTRUCT()
struct FEffectProperties
{GENERATED_BODY()FEffectProperties(){}FGameplayEffectContextHandle EffectContextHandle;UPROPERTY()UAbilitySystemComponent* SourceASC = nullptr;UPROPERTY()AActor* SourceAvatarActor = nullptr;UPROPERTY()AController* SourceController = nullptr;UPROPERTY()ACharacter* SourceCharacter = nullptr;UPROPERTY()UAbilitySystemComponent* TargetASC = nullptr;UPROPERTY()AActor* TargetAvatarActor = nullptr;UPROPERTY()AController* TargetController = nullptr;UPROPERTY()ACharacter* TargetCharacter = nullptr;
};/*** 技能系统属性集*/
UCLASS()
class AURA_API UAttributeSetBase : public UAttributeSet
{GENERATED_BODY()public:UAttributeSetBase();virtual void GetLifetimeReplicatedProps(TArray<FLifetimeProperty>& OutLifetimeProps) const override;virtual void PreAttributeChange(const FGameplayAttribute& Attribute, float& NewValue) override;virtual void PostGameplayEffectExecute(const FGameplayEffectModCallbackData& Data) override;UPROPERTY(BlueprintReadOnly,ReplicatedUsing = OnRep_Health, Category="Vital Attributes")FGameplayAttributeData Health;ATTRIBUTE_ACCESSORS(UAttributeSetBase, Health);UPROPERTY(BlueprintReadOnly,ReplicatedUsing = OnRep_MaxHealth, Category="Vital Attributes")FGameplayAttributeData MaxHealth;ATTRIBUTE_ACCESSORS(UAttributeSetBase, MaxHealth);UPROPERTY(BlueprintReadOnly,ReplicatedUsing = OnRep_Mana, Category="Vital Attributes")FGameplayAttributeData Mana;ATTRIBUTE_ACCESSORS(UAttributeSetBase, Mana);UPROPERTY(BlueprintReadOnly,ReplicatedUsing = OnRep_MaxMana, Category="Vital Attributes")FGameplayAttributeData MaxMana;ATTRIBUTE_ACCESSORS(UAttributeSetBase, MaxMana);UFUNCTION()void OnRep_Health(const FGameplayAttributeData& OldHealth) const;UFUNCTION()void OnRep_MaxHealth(const FGameplayAttributeData& OldMaxHealth) const;UFUNCTION()void OnRep_Mana(const FGameplayAttributeData& OldMana) const;UFUNCTION()void OnRep_MaxMana(const FGameplayAttributeData& OldMaxMana) const;private:static void SetEffectProperties(const FGameplayEffectModCallbackData& Data, FEffectProperties& Props);
};

AttributeSetBase.cpp

// 版权归暮志未晚所有。#include "AbilitySystem/AttributeSetBase.h"#include "AbilitySystemBlueprintLibrary.h"
#include "GameplayEffectExtension.h"
#include "GameFramework/Character.h"
#include "Net/UnrealNetwork.h"UAttributeSetBase::UAttributeSetBase()
{InitHealth(30.f);InitMaxHealth(100.f);InitMana(30.f);InitMaxMana(100.f);
}void UAttributeSetBase::GetLifetimeReplicatedProps(TArray<FLifetimeProperty>& OutLifetimeProps) const
{Super::GetLifetimeReplicatedProps(OutLifetimeProps);DOREPLIFETIME_CONDITION_NOTIFY(UAttributeSetBase, Health, COND_None, REPNOTIFY_Always);DOREPLIFETIME_CONDITION_NOTIFY(UAttributeSetBase, MaxHealth, COND_None, REPNOTIFY_Always);DOREPLIFETIME_CONDITION_NOTIFY(UAttributeSetBase, Mana, COND_None, REPNOTIFY_Always);DOREPLIFETIME_CONDITION_NOTIFY(UAttributeSetBase, MaxMana, COND_None, REPNOTIFY_Always);
}void UAttributeSetBase::PreAttributeChange(const FGameplayAttribute& Attribute, float& NewValue)
{Super::PreAttributeChange(Attribute, NewValue);if(Attribute == GetHealthAttribute()){NewValue = FMath::Clamp(NewValue, 0.f, GetMaxHealth());// UE_LOG(LogTemp, Warning, TEXT("Health: %f"), NewValue);}if(Attribute == GetManaAttribute()){NewValue = FMath::Clamp(NewValue, 0.f, GetMaxMana());}
}void UAttributeSetBase::SetEffectProperties(const FGameplayEffectModCallbackData& Data, FEffectProperties& Props)
{//Source 效果的所有者   Target 效果应用的目标Props.EffectContextHandle = Data.EffectSpec.GetContext();Props.SourceASC = Props.EffectContextHandle.GetOriginalInstigatorAbilitySystemComponent(); //获取效果所有者的ASC//获取效果所有者的相关对象if(IsValid(Props.SourceASC) && Props.SourceASC->AbilityActorInfo.IsValid() && Props.SourceASC->AbilityActorInfo->AvatarActor.IsValid()){Props.SourceAvatarActor = Props.SourceASC->AbilityActorInfo->AvatarActor.Get(); //获取ActorProps.SourceController = Props.SourceASC->AbilityActorInfo->PlayerController.Get(); //获取PlayerControllerif(Props.SourceController == nullptr && Props.SourceAvatarActor != nullptr){if(const APawn* Pawn = Cast<APawn>(Props.SourceAvatarActor)){Props.SourceController = Pawn->GetController();}}if(Props.SourceController){Props.SourceCharacter = Cast<ACharacter>(Props.SourceController->GetPawn());}}if(Data.Target.AbilityActorInfo.IsValid() && Data.Target.AbilityActorInfo->AvatarActor.IsValid()){Props.TargetAvatarActor = Data.Target.AbilityActorInfo->AvatarActor.Get();Props.TargetController = Data.Target.AbilityActorInfo->PlayerController.Get();Props.TargetCharacter = Cast<ACharacter>(Props.TargetAvatarActor);Props.TargetASC = UAbilitySystemBlueprintLibrary::GetAbilitySystemComponent(Props.TargetAvatarActor);}
}void UAttributeSetBase::PostGameplayEffectExecute(const FGameplayEffectModCallbackData& Data)
{Super::PostGameplayEffectExecute(Data);FEffectProperties Props;SetEffectProperties(Data, Props);
}void UAttributeSetBase::OnRep_Health(const FGameplayAttributeData& OldHealth) const
{GAMEPLAYATTRIBUTE_REPNOTIFY(UAttributeSetBase, Health, OldHealth);
}void UAttributeSetBase::OnRep_MaxHealth(const FGameplayAttributeData& OldMaxHealth) const
{GAMEPLAYATTRIBUTE_REPNOTIFY(UAttributeSetBase, MaxHealth, OldMaxHealth);
}void UAttributeSetBase::OnRep_Mana(const FGameplayAttributeData& OldMana) const
{GAMEPLAYATTRIBUTE_REPNOTIFY(UAttributeSetBase, MaxHealth, OldMana);
}void UAttributeSetBase::OnRep_MaxMana(const FGameplayAttributeData& OldMaxMana) const
{GAMEPLAYATTRIBUTE_REPNOTIFY(UAttributeSetBase, MaxHealth, OldMaxMana);
}