UE5 C++ GameInstanceSubsystem 在学习

一.子系统概述

参考官方文档

虚幻引擎编程子系统 | 虚幻引擎 5.7 文档 | Epic Developer Community

游戏实例子系统是子系统中的一种，目前用最多。编辑器的更多涉及到编辑器开发。

更多优点，去看大钊的文章。

二.子系统生命周期的优势在关卡切换中

子系统几乎和引擎同步，所以游戏里喜欢把核心的跨关卡的数据放到子系统里保存管理。一是方便获得，蓝图直接拿，C++有模块包个头就能用，爽，进而修改同步。二是生命周期够长，即使是切换关卡后，也许物体没了，但子系统里的数据依然保留，方法指针等也会保留。也方便做后续的类似存档，读档。

以下是案例

在关卡蓝图里，调用子系统里的东西。

Map1 +11

Map2 +11

切换关卡，依然会执行。

三.子系统与多播

通过子系统方便全局获得委托，并且进行绑定和呼叫执行。它俩简直绝配。

以下是案例。

cpp 复制代码

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

#pragma once

#include "CoreMinimal.h"
#include "Subsystems/GameInstanceSubsystem.h"
#include "GWXGameInstanceSubsystem.generated.h"

DECLARE_DYNAMIC_MULTICAST_DELEGATE_TwoParams(FWXSubsystemLocation, FString ,InActionName, int32 ,InActionIndexTime);
/**
 * 
 */
//UGWXGameInstanceSubsystem* UGWXGameInstanceSubsystem::MySubsystem = nullptr;

UCLASS()
class THIRDLEARN_API UGWXGameInstanceSubsystem : public UGameInstanceSubsystem
{
	GENERATED_BODY()

public:

	virtual bool ShouldCreateSubsystem(UObject* Outer) const override;

	/** Implement this for initialization of instances of the system */
	virtual void Initialize(FSubsystemCollectionBase& Collection)override;

	/** Implement this for deinitialization of instances of the system */
	virtual void Deinitialize()override;

	UFUNCTION(BlueprintCallable)
	void CallLocation(FString InActionName,int32 InActionIndex);

	UFUNCTION(BlueprintCallable)
	UGWXGameInstanceSubsystem* GetGWXSubsystemself();

	UPROPERTY(BlueprintAssignable)
	FWXSubsystemLocation WXSubsystemLocationDelegate;

	void AddHealth(int num);

private:
	//static UGWXGameInstanceSubsystem* MySubsystem;
	int Health = 0;
};

cpp 复制代码

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


#include "GWXGameInstanceSubsystem.h"



bool UGWXGameInstanceSubsystem::ShouldCreateSubsystem(UObject* Outer) const
{
	return true;
}

void UGWXGameInstanceSubsystem::Initialize(FSubsystemCollectionBase& Collection)
{
	Super::Initialize(Collection);
	//MySubsystem = this;
}

void UGWXGameInstanceSubsystem::Deinitialize()
{
	//MySubsystem = nullptr;
	Super::Deinitialize();
}

void UGWXGameInstanceSubsystem::CallLocation(FString InActionName, int32 InActionIndex)
{
	WXSubsystemLocationDelegate.Broadcast(InActionName, InActionIndex);
}

UGWXGameInstanceSubsystem* UGWXGameInstanceSubsystem::GetGWXSubsystemself()
{
	//return MySubsystem;
	return nullptr;
}

void UGWXGameInstanceSubsystem::AddHealth(int num)
{
	Health += num;
}

在关卡蓝图中，通过子系统呼叫

在Actor里，通过子系统，绑定。很轻松就完成跨类委托

四.获得子系统的多种方式

A类获取，可以直接GetGameInstance->GetSubsystem获取

cpp 复制代码

void AGWXGamieInstance_TestActor::BeginPlay()
{
	Super::BeginPlay();
	UGameInstance* MyGameInstance = GetGameInstance();
	if (MyGameInstance)
	{
		UGWXGameInstanceSubsystem* MySimpleSubsystem = MyGameInstance->GetSubsystem<UGWXGameInstanceSubsystem>();
		MySimpleSubsystem->AddHealth(998);
	}
}

U类获取,需要获得World,再拿到GetGameInstance->GetSubsystem获取

cpp 复制代码

void AGWXGamieInstance_TestActor::ObjectGetSubsystem(const UObject* InWorldContextObject)
{
	if (InWorldContextObject && InWorldContextObject->GetWorld())
	{
		UGameInstance* MyGameInstace = InWorldContextObject->GetWorld()->GetGameInstance();
		if (MyGameInstace)
		{
			UGWXGameInstanceSubsystem* MySimpleSubsystem = MyGameInstace->GetSubsystem<UGWXGameInstanceSubsystem>();
			MySimpleSubsystem->AddHealth(2000);
		}
	}
}

传统static 获取，会有安全隐患

头文件

cpp 复制代码

	UFUNCTION(BlueprintCallable)
	static UGWXGameInstanceSubsystem* GetXGSubsystemMySelf();



private:
	int32 CurrentHealth = 100;
	bool bFirstTick = true;

	static UGWXGameInstanceSubsystem* MySubsystemPtr;

源文件，跟随生命周期赋值。

cpp 复制代码

#include "GWXGameInstanceSubsystem.h"

UGWXGameInstanceSubsystem* UGWXGameInstanceSubsystem::MySubsystemPtr = nullptr;

void UGWXGameInstanceSubsystem::Initialize(FSubsystemCollectionBase& Collection)
{
	Super::Initialize(Collection);
	MySubsystemPtr = this;
}

void UGWXGameInstanceSubsystem::Deinitialize()
{
	MySubsystemPtr = nullptr;
	Super::Deinitialize();
}

UGWXGameInstanceSubsystem* UGWXGameInstanceSubsystem::GetXGSubsystemMySelf()
{
	return MySubsystemPtr;
}

其他类测试

复制代码

	UGWXGameInstanceSubsystem* MySimpleSubsystem = UGWXGameInstanceSubsystem::GetXGSubsystemMySelf();
	MySimpleSubsystem->AddHealth(666);

五.子系统的Tick

很简单在子系统里集成一个public FTickableGameObject类，重写Tick就行。还有些其它函数也可重写，如

cpp 复制代码

	virtual void Tick(float DeltaTime) override;

	virtual bool IsTickable() const override;

	virtual TStatId GetStatId() const override;

然后

cpp 复制代码

void UGWXGameInstanceSubsystem::Tick(float DeltaTime)  //无需super 虚方法
{
	UE_LOG(LogTemp,Warning,TEXT("12345"));
}

bool UGWXGameInstanceSubsystem::IsTickable() const
{
	return !IsTemplate();
}

TStatId UGWXGameInstanceSubsystem::GetStatId() const
{
	RETURN_QUICK_DECLARE_CYCLE_STAT(UGWXGameInstanceSubsystem, STATGROUP_Tickables);
}

就能每帧执行一次