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UE(6):UObject和UGameInstance的实例化

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UObject的实例化

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// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "Engine/Classes/Engine/DataTable.h"
#include "UObject/NoExportTypes.h"
#include "MyObject.generated.h"

USTRUCT(BlueprintType)
struct FMyDataTableStruct: public FTableRowBase
{
	GENERATED_USTRUCT_BODY()
	// 声明构造函数
	FMyDataTableStruct();

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MyTestDataTableStruct")
		float Health;
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MyTestDataTableStruct")
		FString Name;
	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "MyTestDataTableStruct")
		int Level;
};

/**
 * 
 */
UCLASS()
class MYPROJECT2_API UMyObject : public UObject
{
	GENERATED_BODY()
public:
    // 声明结构体
	UPROPERTY()
		FMyDataTableStruct MyDataTableStruct;
};

// MyObject.cpp
// 实现构造函数
FMyDataTableStruct::FMyDataTableStruct()
{
	Health = 10.0f;
	Name = TEXT("zhangsan");
	Level = 1;
}

// MyPawn.h
// 声明变量
UPROPERTY()
UMyObject* MyTestObject;

// MyPawn.cpp
void AMyPawn::BeginPlay()
{
	Super::BeginPlay();
	
	TSubclassOf<UMyObject> MySubClassObject = UMyObject::StaticClass();
    // Object实例化
	MyTestObject = NewObject<UMyObject>(GetWorld(), MySubClassObject);
	// 判断是否实例化成功
	if (MyTestObject) {
		UE_LOG(LogTemp, Warning, TEXT("MyTestObject is %s"), *MyTestObject->GetName());
        // 获取结构体变量
		UE_LOG(LogTemp, Warning, TEXT("My Health is %f"), MyTestObject->MyDataTableStruct.Health);
		UE_LOG(LogTemp, Warning, TEXT("My Name is %s"), *MyTestObject->MyDataTableStruct.Name);
		UE_LOG(LogTemp, Warning, TEXT("My Level is %d"), MyTestObject->MyDataTableStruct.Level);
	}
}

image-20240821152243312

UGameInstance的实例化

GameInstance全局唯一单例，这个在引擎初始化的时候就已经生成，一直存在到引擎关闭

作用：

  1. 引擎初始化与关闭时执行的逻辑
  2. 为游戏保全全局数据：比如上一个关卡的信息需要在下一个关卡使用时我们用 GameInstance 保存数据但是只是临时数据，游戏结束则消失，如果想要本地持久保存数据需要用 SaveGame

引擎中创建 MyGameInstance 类

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// MyGameInstance.h
// 类中声明
public:
	// 声明构造函数
	UMyGameInstance();
	UPROPERTY(EditAnyWhere, BlueprintReadWrite, Category = "MyInstance")
		FString MyAPPID;
	UPROPERTY(EditAnyWhere, BlueprintReadWrite, Category = "MyInstance")
		FString MyUserID;
	UPROPERTY(EditAnyWhere, BlueprintReadWrite, Category = "MyInstance")
		FString MyName;

// MyGameInstance.cpp
// 实现构造函数
UMyGameInstance::UMyGameInstance()
{
	MyAPPID = TEXT("123");
	MyUserID = TEXT("456");
	MyName = TEXT("zhangsan");
}

// MyPawn.h
#include "MyGameInstance.h"
// 声明一个Instance变量
UPROPERTY()
    UMyGameInstance* MyInstance;

// MyPawn.cpp
// MyInstance实例化
MyInstance = Cast<UMyGameInstance>(GetWorld()->GetFirstLocalPlayerFromController()->GetGameInstance());
if (MyInstance) {
    UE_LOG(LogTemp, Warning, TEXT("MyInstance is %s"), *MyInstance->GetName());
    UE_LOG(LogTemp, Warning, TEXT("MyAPPID is %s"), *MyInstance->MyAPPID);
    UE_LOG(LogTemp, Warning, TEXT("MyUserID is %s"), *MyInstance->MyUserID);
    UE_LOG(LogTemp, Warning, TEXT("MyName is %s"), *MyInstance->MyName);
}

运行

编辑—>项目设置—>地图与模式—>游戏实例—>游戏实例类—>MyGameInstance

image-20240821170426505