以下示例展示了国王被杀后，农民惊呀的场景

第一步，创建King类

• DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam为声明委托
  • FOnKingDeathSignature为委托类型
  • AKing* 为输入参数

#pragma once
#include "CoreMinimal.h"
#include "Engine/StaticMeshActor.h"
#include "King.generated.h"

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FOnKingDeathSignature, AKing*, DeadKing);

UCLASS()
class UEPROJ_API AKing : public AStaticMeshActor
{
	GENERATED_BODY()
public:
	AKing();

    UFUNCTION(BlueprintCallable, Category = King)
    void Die();

    UPROPERTY(BlueprintAssignable)
    FOnKingDeathSignature OnKingDeath;
};

#include "King.h"
#include "UObject/ConstructorHelpers.h"

AKing::AKing()
{
    PrimaryActorTick.bCanEverTick = true;
    auto MeshAsset = ConstructorHelpers::FObjectFinder<UStaticMesh>(TEXT("StaticMesh'/Engine/BasicShapes/Cone.Cone'"));
    if (MeshAsset.Object != nullptr)
    {
        GetStaticMeshComponent()->SetStaticMesh(MeshAsset.Object);
        GetStaticMeshComponent()->SetGenerateOverlapEvents(true);
    }
    GetStaticMeshComponent()->SetMobility(EComponentMobility::Movable);
}

void AKing::Die()
{
    OnKingDeath.Broadcast(this);
}

第二步，创建Peasant类

#pragma once
#include "CoreMinimal.h"
#include "Engine/StaticMeshActor.h"
#include "Peasant.generated.h"

UCLASS()
class UEPROJ_API APeasant : public AStaticMeshActor
{
	GENERATED_BODY()
	
	APeasant();

    UFUNCTION(BlueprintCallable, category = Peasant)
    void Flee(AKing* DeadKing);
};

#include "Peasant.h"
#include "UObject/ConstructorHelpers.h"
#include "King.h"

APeasant::APeasant()
{
    auto MeshAsset = ConstructorHelpers::FObjectFinder<UStaticMesh>(TEXT("StaticMesh'/Engine/BasicShapes/Cube.Cube'"));
    if (MeshAsset.Object != nullptr)
    {
        GetStaticMeshComponent()->SetStaticMesh(MeshAsset.Object);
        GetStaticMeshComponent()->SetGenerateOverlapEvents(true);
    }
    GetStaticMeshComponent()->SetMobility(EComponentMobility::Movable);
}

void APeasant::Flee(AKing* DeadKing)
{
    auto actorLabel = this->GetActorLabel();
    auto msg = FString::Printf(TEXT("%s Waily！"), *actorLabel);
    GEngine->AddOnScreenDebugMessage(-1, 2, FColor::Red, msg);

    FVector FleeVector = GetActorLocation() - DeadKing->GetActorLocation();
    FleeVector.Normalize();
    FleeVector *= 500;
    SetActorLocation(GetActorLocation() + FleeVector);
}

基于Peasant创建一个蓝图类，名为：BPPeasant

然后编辑此蓝图

• 从BeginPlay开始，接一个新节点，Get All Actors Of Class
  • 【注意】 拉节点时，要把Context Sensitive的勾去掉，否则找不到 Get All Actors Of Class
  • 在Actor Class中，选择King类

• 最出第1个King，在Out Actors输出端，接 Get (a copy) 节点

• 为了防止取出的节点为空，所以要添加为空判断，所以 Get All Actors Of Class 后续要添加判断语句，添加Branch节点

• Branch要添加Condition，所以添加一个前置节点NotEqual(object)节点

• Get(a copy)输出为 NotEqual(object)的输入，NotEqual(object)的第2个节点不选

• GetAllActorsOfClass后续接Branch节点

• 综上所述：以上语句为了实现 if ( GetAllAlctorsOfClass[0] != null) 的功能

• Branch 后续添加节点：Bine Event to On King Death
  • Target 为 Get (a copy) 节点 的输出

• Bine Event to On King Death 添加 事件， 选择 自定义事件（Add Custom Event … ),名为 KingIsDeadEvent

• KingIsDeadEvent后续接节点 Flee，即为农夫自己执行动作

• Flee的DeadKing为 KingIsDeadEvent 的输出节点 Dead King

然后在场景中创建一个King，四周创建几个BPPeasant。

编辑关卡蓝图

把King扔进去，2秒后，让它死，如上图所示

然后运行游戏，看表现。