Guide de démarrage rapide des Event Dispatchers et délégués

Overview

Delegates can call methods in Actor class Blueprints in a type-safe way. A delegate can be bound dynamically to form a communication where one Actor triggers an event on another Actor that is listening to be notified for that event.

Goals

In this Quick Start guide, you will learn how to use Delegates to create an OnBossDied event that will trigger two Actor class Blueprints in your Level.

Objectives

• Create the Boss Actor that will contain an OnBossDied Delegate.

• Create an interactive door Actor with a timeline component that will bind to the OnBossDied event.

1 - Required Setup

1. In the New Project Categories section of the menu, select Games and click Next.

   

2. Select the Third Person template and click Next.

   

3. Select the C++ and With Starter Content options and click Create Project.

   

Section Results

You have created a new C++ Third Person project and are now ready to learn about Delegates.

2 - Creating the Boss Actor and OnBossDied Delegate

1. From the C++ Class Wizard, create a new Actor class named BossActor.

   

2. Navigate to your BossActor.h. Underneath your library includes, declare the following Delegate.

   C++

   DECLARE_DELEGATE(FOnBossDiedDelegate);

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3. In your class defaults, declare the following

   C++

   protected:
                UFUNCTION()
                void HandleBossDiedEvent();
                UPROPERTY(EditInstanceOnly, BlueprintReadWrite)
                class UBoxComponent* BoxComp;
                virtual void NotifyActorBeginOverlap(AActor* OtherActor);
   		
            public:
                FOnBossDiedDelegate OnBossDied;

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4. Navigate to your BossActor.cpp and add the following class library.

   C++

   #include "Components/BoxComponent.h"

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5. Implement the following class definitions.

   C++

   ABossActor::ABossActor()
            {
                BoxComp = CreateDefaultSubobject<UBoxComponent>(TEXT("BoxComp"));
                BoxComp->SetBoxExtent(FVector(128, 128, 64));
                BoxComp->SetVisibility(true);
            }
   		
            void ABossActor::HandleBossDiedEvent()
            {
                OnBossDied.ExecuteIfBound();
   
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6. Compile your code.

7. From the C++ Classes folder, right-click your BossActor, then from the C++ Class Actions dropdown menu, select Create Blueprint class based on BossActor. Name your Blueprint class BP_BossActor.

   

8. Drag an instance of your BossActor into the Level.

   

Finished Code

BossActor.h

#pragma once
	#include "CoreMinimal.h"
	#include "GameFramework/Actor.h"
	#include "BossActor.generated.h"

	DECLARE_DELEGATE(FOnBossDiedDelegate);
	UCLASS()

	class BPCOMMUNICATION_API ABossActor : public AActor
	{

BossActor.cpp

#include "BossActor.h"
	#include "Components/BoxComponent.h"
	#include "BPCommunicationGameMode.h"

	// Sets default values
	ABossActor::ABossActor()
	{
		// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
		PrimaryActorTick.bCanEverTick = true;
		BoxComp = CreateDefaultSubobject<UBoxComponent>(TEXT("BoxComp"));

Section Results

In this section you created the BossActor class, which contains a Box Component, and Delegate for a OnBossDied event, which will be used to signal other Actor classes when the event has been executed.

3 - Creating an Interactive Door

1. From the C++ Class Wizard, create a new Actor class named DoorActor.

2. Navigate to your DoorActor.h file and declare the following include:

   C++

   #include "Components/TimelineComponent.h"

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3. Then declare the following class definitions.

   C++

   // Variable to hold the Curve asset
                UPROPERTY(EditInstanceOnly)
                UCurveFloat* DoorTimelineFloatCurve;
   		
            protected:
   		
                void BossDiedEventFunction();
                UPROPERTY(EditInstanceOnly,BlueprintReadWrite)
                class ABossActor* BossActorReference;
   		
   
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4. Inside of DoorActor.cpp declare the following class library.

   C++

   #include "BossActor.h"

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5. Implement the following class definitions.

   C++

   ADoorActor::ADoorActor()
           {
               //Create our Default Components
               DoorFrame = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("DoorFrameMesh"));
               Door = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("DoorMesh"));
               DoorTimelineComp = CreateDefaultSubobject<UTimelineComponent>(TEXT("DoorTimelineComp"));
   		
               //Setup our Attachments
               DoorFrame->SetupAttachment(RootComponent);
               Door->AttachToComponent(DoorFrame, FAttachmentTransformRules::KeepRelativeTransform);
   
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6. Compile your code.

7. From the Content Browser, select Add/Import > Miscellaneous > Curve.

   

8. Select CurveFloat and name your CurveFloat asset DoorCurveFloat, then double-click your DoorCurveFloat asset. Add two keys to your Float Curve and give one key the time-value (0,0), and the other key the time-value of (4,90).

   

9. Shift-click to select both your keys, and set them to Auto Cubic interpolation, then save your Curve.

   

10. Save your DoorCurveFloat.

11. From the Content Browser, navigate to your C++ Classes folder, right-click your DoorActor class, then select Create Blueprint Class based on Door Actor. Name your Blueprint Actor Bp_DoorActor.

    

12. Inside BP_DoorActor's class defaults, find the Components tab, and select the DoorFrame Static Mesh component, navigate to the Details panel and change the Static Mesh to SM_DoorFrame.

    

13. Next, from the Components tab, select the DoorMesh component. Navigate to the Details panel and change the static mesh to SM_Door.

    

14. From the Details panel, select DoorCurveFloat from the Door Timeline Float Curve dropdown menu.

    

15. Compile and save your Blueprint.

Finished Code

DoorActor.h

#include "CoreMinimal.h"
	#include "GameFramework/Actor.h"
	#include "Components/TimelineComponent.h"
	#include "DoorActor.generated.h"

	UCLASS()
	class BPCOMMUNICATION_API ADoorActor : public AActor
	{
		GENERATED_BODY()

DoorActor.cpp

#include "DoorActor.h"
	#include "BossActor.h"

	// Sets default values
	ADoorActor::ADoorActor()
	{
		// Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
		PrimaryActorTick.bCanEverTick = true;

		//Create our Default Components

Section Results

In this section you created an interactive DoorActor that binds to the OnBossDied Event Dispatcher found in the BossActor class. This binding occurs in Begin Play, but is executed at runtime whenever this event is triggered by an overlap in BossActor's Box Component.

5 - Testing the Event Dispatcher

1. Drag the BP_Door Blueprint into your Level. Go to the Details panel and click the Boss Reference Died dropdown and search for and select BP_BossDied.

   

2. With your Bp_DoorActor selected, navigate to the Details panel, click the Boss Actor Reference dropdown arrow, then search for and select BP_BossActpr.

3. Press Play and walk over the BP_BossActor trigger to simulate your boss dying in the game.

   

Section Results

In this section you tested the BP_DoorActor in the Level. You confirmed that the Actor responds to the OnBossDied event when the BP_BossActor's Box Component overlaps with another Actor to trigger the Delegate.

In this guide you learned how to use Delegates to communicate between multiple Actor class Blueprints.

Next Steps

Now that you know how to use Delegates, take a look at the other communication types referenced in the documentation page.