Unreal Engine C++ Interfaces

Implementing Simple Interface

Introduction 

Interface : We need sometime common functionality in our  game-play classes so we define here some functionality or other working objects and implement it a require game-play classes.
In C++ we use multiple inheritance to solve this.

Unreal Engine provide Interface more power of our game-play classes with Blueprint accessible macros;

Require :
Visual Studio 2019
Unreal Engine 4.22
C++ Project

Creating a UInterface 

Add New > New C++ Class > Scroll Down Class >Unreal  UInterface > Next > name it!!

Now you can see This type of code
.h file
#pragma once

#include "CoreMinimal.h"
#include "UObject/Interface.h"
#include "MyFirstInterface.generated.h"

// This class does not need to be modified.
UINTERFACE(MinimalAPI)
class UMyFirstInterface : public UInterface
{
GENERATED_BODY()
};

/**
 *
 */
class COVERTRACK_API IMyFirstInterface
{
GENERATED_BODY()

// Add interface functions to this class. This is the class that will be inherited to implement this interface.
public:
     
       virtual FString GetName();


};

In .cpp


#include "MyFirstInterface.h"

// Add default functionality here for any IMyFirstInterface functions that are not pure virtual.

FString IMyFirstInterface::GetName() {
unimplemented();
return FString();
}


Compile!!

Implement UInterface 

Now we implement the function we define in Interface and implement in game-play class;

Make a Actor Class 
already have or if not Make it from New C++ class > Actor 

youractor.h 
#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "MyFirstInterface.h"
#include "ES_SpawanEnemy.generated.h"

UCLASS()
class COVERTRACK_API AES_SpawanEnemy : public AActor, public IMyFirstInterface
{
GENERATED_BODY()

public:
// Sets default values for this actor's properties
AES_SpawanEnemy();

protected:
// Called when the game starts or when spawned

virtual void BeginPlay() override;

.h file
public:


   FString GetName() override ;

.cpp

FString AES_SpawanEnemy::GetName()
{
return IMyFirstInterface::GetName();

}

compile!!

Checking Interface working or not

Open GameMode Class 


#include "CoverTrackGameModeBase.h"
#include "ES_SpawanEnemy.h"
#include "MyFirstInterface.h"
#include "Engine/Engine.h"

void ACoverTrackGameModeBase::BeginPlay() {
Super::BeginPlay();

FTransform SpawanLocation;
AES_SpawanEnemy* SpawanActor = GetWorld()->SpawnActor<AES_SpawanEnemy>
(AES_SpawanEnemy::StaticClass(), SpawanLocation);

UClass* ActorClass = SpawanActor->GetClass();

if (ActorClass->ImplementsInterface(UMyFirstInterface::StaticClass()))
{
if (GEngine)
{
GEngine->AddOnScreenDebugMessage(-1, 15.0f, FColor::Red, TEXT("Interface Working"));
}

}
}