Casting to a UInterface implemented in native code

What does this topic explains?
Actually I am studying unreal engine with “Ue4 Scripting with c++ cookbook” by PACKT publication.
And I can’t understand what this topic is trying to explain…

See the topic under this heading “Casting to a UInterface implemented in native code”

Casting to a UInterface implemented in native code

One advantage that UInterfaces provide you with as a developer is the ability to treat a collection of heterogeneous objects that implement a common interface as acollection of the same object, using Cast< > to handle the conversion.

Getting ready You should have a UInterface and an Actor implementing the interface ready for this recipe.
Create a new game mode using the wizard within Unreal, or reuse a project and GameMode from a previous recipe.
How to do it…
Open your game mode’s declaration and add a new property to the class:

UCLASS() class CHAPTER_07_API AChapter_07GameModeBase : public AGameModeBase {     GENERATED_BODY() public:
    virtual void BeginPlay() override;
    TArray<IMyInterface*> MyInterfaceInstances;

Add #include “MyInterface.h” to the header’s include section:

#pragma once #include "CoreMinimal.h"
#include "GameFramework/GameModeBase.h"
#include "MyInterface.h"
#include "Chapter_07GameModeBase.generated.h"

Add the following within the game mode’s BeginPlay implementation:

for (TActorIterator<AActor> It(GetWorld(), AActor::StaticClass());  It;  ++It) 
    AActor* Actor = *It;
    IMyInterface* MyInterfaceInstance = Cast<IMyInterface>(Actor);
// If the pointer is valid, add it to the list    
 if (MyInterfaceInstance)   
 // Print out how many objects implement the interface 
FString Message = FString::Printf(TEXT("%d actors implement the interface"), MyInterfaceInstances.Num());
GEngine->AddOnScreenDebugMessage(-1, 10, FColor::Red, Message);

Since we are using the TActorIterator class, we will need to add the following #include to the top of our GameModeBase class’ implementation file:

#include "EngineUtils.h" 

// TActorIterator If you haven’t done so already, set the level’s game mode override to your5.
game mode, then drag a few instances of your custom Interfaceimplementing actor into the level.
When you play your level, a message should be printed on screen that.
indicates the number of instances of the interface that have been implemented in Actors in the level: