▼代码开始
// Fill out your copyright notice in the Description page of Project Settings.#pragma once#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "sand.h"
#include "MyActor.generated.h"UCLASS()
class EMPTY_API AMyActor : public AActor
{GENERATED_BODY()public:    // Sets default values for this actor's properties
    AMyActor();protected:// Called when the game starts or when spawnedvirtual void BeginPlay() override;public:    // Called every framevirtual void Tick(float DeltaTime) override;UPROPERTY()TArray<Asand* > arr;//【注意最好有UPROPERTY()标注】
    };
▲代码结束▼代码开始
// Fill out your copyright notice in the Description page of Project Settings.

#include "MyActor.h"// Sets default values
AMyActor::AMyActor()
{// 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;}// Called when the game starts or when spawned
void AMyActor::BeginPlay()
{Super::BeginPlay();for (auto i = 0; i < 4; i++){Asand* newSand = GetWorld()->SpawnActor<Asand>(Asand::StaticClass());//【SpawnActor的方法】arr.Add(newSand);//【Add的方法】UE_LOG(LogTemp, Warning, TEXT("%s"), *FString("[log by wenjie] i ve added a sand tinto arr"));//【打印的方法】
    }}// Called every frame
void AMyActor::Tick(float DeltaTime)
{Super::Tick(DeltaTime);static int32 Timer = 0;if (Timer++ == 20){UE_LOG(LogTemp, Warning, TEXT("%s"), *FString("[log by wenjie] Time==20"));
/*
不正确的方法：for (auto i : arr){//【不建议的remove方法】arr.Remove(i);UE_LOG(LogTemp, Warning, TEXT("%s"), *FString("[log by wenjie] removed one instance"));}上面的remove的方法不十分优雅：
在执行过程中报如下错误【可能死机也可能不死机】：
LogOutputDevice:Error: === Handled ensure: ===
LogOutputDevice:Error: Ensure condition failed: Lhs.CurrentNum == Lhs.InitialNum [File:D:\UE4.16.3\UE_4.16\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 197]
LogOutputDevice:Error: Array has changed during ranged-for iteration!以下提供恰当的remove方法：
//参考资料：
//https://forums.unrealengine.com/showthread.php?69383-A-Little-Tip-Remove-elements-from-an-array-in-one-pass-with-a-reverse-for-loop
*/for (auto i = arr.Num() - 1; i >= 0; i--){arr.RemoveAt(i);UE_LOG(LogTemp, Warning, TEXT("%s"), *FString("[log by wenjie] removed one instance"));}}
}▲代码结束