UE4 基于GAS的插件ArcInventory拆解-1_库存核心：ArcInventoryComponent、FArcInventoryItemSlot

女爷i 2022-09-10 10:24 114阅读 0赞

# 零、资料 #

插件地址：  
[https://www.unrealengine.com/marketplace/zh-CN/product/arc-inventory][https_www.unrealengine.com_marketplace_zh-CN_product_arc-inventory]  
文档地址:  
[https://redirect.epicgames.com/?redirectTo=https://punyhumangames.github.io/ArcPluginsDocumentation/arcinventory/][https_redirect.epicgames.com_redirectTo_https_punyhumangames.github.io_ArcPluginsDocumentation_arcinventory]

# 一、`UArcInventoryComponent` #

## 1.1 主要属性 ##

FArcInventoryItemSlotArray BagInventory;
    	TArray<FArcInventoryItemSlotReference> AllReferences;

> 确定了InventoryComp的核心：背包

### 1.1.1 `BagInventory` ###

**这是存储所有库存的地方，只具有储存的同步功能**

**结构体定义：**

USTRUCT()
    struct FArcInventoryItemSlotArray : public FFastArraySerializer
    {
        
    	GENERATED_USTRUCT_BODY()
    public:
    
    	UPROPERTY()
    	TArray< FArcInventoryItemSlot> Slots;
    
    	UPROPERTY()
    	UArcInventoryComponent* Owner;
    
    	bool NetDeltaSerialize(FNetDeltaSerializeInfo& DeltaParms)
    	{
        
    		return FFastArraySerializer::FastArrayDeltaSerialize<FArcInventoryItemSlot, FArcInventoryItemSlotArray>(Slots, DeltaParms, *this);
    	}
    };

**主要负责存储插槽数组，并使用了`FFastArraySerializer`来优化结构体数组的同步问题**

**FFastArraySerializer资料:**  
官方文档  
[https://docs.unrealengine.com/4.27/en-US/API/Runtime/Engine/Engine/FFastArraySerializer/][https_docs.unrealengine.com_4.27_en-US_API_Runtime_Engine_Engine_FFastArraySerializer]  
UE4Guide  
[https://ikrima.dev/ue4guide/networking/network-replication/fast-tarray-replication/][https_ikrima.dev_ue4guide_networking_network-replication_fast-tarray-replication]

### 1.1.2、`AllReferences` ###

**作用:**  
是外部获取Slot的Handle，包含了所有BagInventory里Slot的引用

//仅仅是主要结构
    USTRUCT(BlueprintType)
    struct ARCINVENTORY_API FArcInventoryItemSlotReference
    {
        
    	GENERATED_USTRUCT_BODY()
    public:
    	//...不同类型的构造函数
    
    	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Inventory)
    		int32 SlotId;
    
    	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = Inventory)
    	FGameplayTagContainer SlotTags;
    
    	UPROPERTY(BlueprintReadWrite, VisibleInstanceOnly, Category = Inventory)
    	class UArcInventoryComponent* ParentInventory;
    
    	bool NetSerialize(FArchive& Ar, class UPackageMap* Map, bool& bOutSuccess);
    	
    	bool operator==(const FArcInventoryItemSlotReference& Other) const;
    	bool operator==(const FArcInventoryItemSlot& Other) const;
    };

**实现**  
通过记录Inventory指针+索引Id来记录Slot引用，方便网络复制以及查找  
相应地，提供==重载简化操作

## 1.2、主要接口 ##

核心函数望文生义：背包基本的增删改查操作

//增
    	UFUNCTION(BlueprintCallable, Category="Arc|Inventory")
    	virtual bool LootItem(UArcItemStack* Item);
    	UFUNCTION(BlueprintCallable, Category = "Arc|Inventory")
    	virtual bool PlaceItemIntoSlot(UArcItemStack* Item, const FArcInventoryItemSlotReference& ItemSlot);
    
    //删
    	UFUNCTION(BlueprintCallable, Category = "Arc|Inventory")
    	virtual bool RemoveItemFromInventory(const FArcInventoryItemSlotReference& ItemSlot);
    	UFUNCTION(BlueprintCallable, Category = "Arc|Inventory")
    	virtual bool RemoveAllItemsFromInventory(TArray<UArcItemStack*>& OutItemsRemoved);
    
    //改(交换)
    	UFUNCTION(BlueprintCallable, Category = "Arc|Inventory")
    	virtual bool SwapItemSlots(const FArcInventoryItemSlotReference& FromSlot, const FArcInventoryItemSlotReference& ToSlot);
    
    //查
    	UFUNCTION(BlueprintCallable, Category = "Arc|Inventory")
    	virtual bool IsValidItemSlot(const FArcInventoryItemSlotReference& Slot);
    
    	UFUNCTION(BlueprintPure, Category = "Arc|Inventory")
    	virtual TArray<FArcInventoryItemSlotReference> GetAllSlotReferences();
    	virtual FArcInventoryItemSlot& GetItemSlot(const FArcInventoryItemSlotReference& RefSlot);
    	virtual UArcItemStack* GetItemInSlot(const FArcInventoryItemSlotReference& Reference);
    	
    	UFUNCTION(BlueprintPure, Category = "Arc|Inventory")
    	virtual int32 GetInventorySize();

### 1.2.1、增 ###

**作用**  
将物品放入背包中，目前是两种方式:放置到固定位置+自动放置到任意符合的位置

bool LootItem(UArcItemStack* Item){
        
    	for (auto Slot : BagInventory.Slots){
        
    		FArcInventoryItemSlotReference SlotRef(Slot, this);
    		if (AcceptsItem(Item, SlotRef) && PlaceItemIntoSlot(Item, SlotRef)){
        
    			return true;}}
    	return false;}
    	
    bool PlaceItemIntoSlot(UArcItemStack* Item, const FArcInventoryItemSlotReference& ItemSlot){
        
    	//1.检查是否能塞进去
    	if (!AcceptsItem(Item, ItemSlot)){
        
    		return false;}
    	if (IsValid(Item) && Item->GetOwner() != GetOwner()){
        
    		UArcItemStack::TransferStackOwnership(Item, GetOwner());}
    	//2.赋值
    	FArcInventoryItemSlot& Slot = GetItemSlot(ItemSlot);
    	UArcItemStack* PreviousItem = Slot.ItemStack;
    	Slot.ItemStack = Item;
    	//3.广播和网络更新
    	BagInventory.MarkItemDirty(Slot);
    	OnInventoryUpdate.Broadcast(this);
    	OnItemSlotChange.Broadcast(this, ItemSlot, Item, PreviousItem);
    	GetOwner()->ForceNetUpdate();
    	return true;
    }

**实现:**  
加入库存的是ItemStack类型，加入方式简单直接。  
ItemStack是ItemSlot的内部储存实现，可以被重载生成自己的插槽类型

### 1.2.2、删 ###

**作用**  
根据Reference删除特定Slot内的元素，或者删除所有元素

bool UArcInventoryComponent::RemoveItemFromInventory(const FArcInventoryItemSlotReference& ItemSlot)
    {
        
    	//1.检查
    	if (!IsValid(ItemSlot)){
        
    		return false;}
    	FArcInventoryItemSlot& Item = GetItemSlot(ItemSlot);
    	UArcItemStack* PreviousItem = Item.ItemStack;
    	if (!IsValid(Item.ItemStack)){
        
    		return false;}
    
    	//2.删除
    	Item.ItemStack = nullptr;
    
    	//3.广播
    	BagInventory.MarkItemDirty(Item);
    	BagInventory.MarkArrayDirty();
    	OnInventoryUpdate.Broadcast(this);
    	OnItemSlotChange.Broadcast(this, ItemSlot, Item.ItemStack, PreviousItem);
    	GetOwner()->ForceNetUpdate();
    	return true;
    }
    
    bool UArcInventoryComponent::RemoveAllItemsFromInventory(TArray<UArcItemStack*>& OutItemsRemoved){
        
    	for (FArcInventoryItemSlot& ItemSlot : BagInventory.Slots){
        
    		if (!IsValid(ItemSlot.ItemStack)){
        
    			continue;}
    		OutItemsRemoved.Add(ItemSlot.ItemStack);
    		RemoveItemFromInventory(FArcInventoryItemSlotReference(ItemSlot, this));}
    	return true;}

**实现:**  
利用Reference进行简单的查询与删除

### 1.2.3、改 ###

**作用:**  
主要是交换逻辑

bool UArcInventoryComponent::SwapItemSlots(const FArcInventoryItemSlotReference& SourceSlot, const FArcInventoryItemSlotReference& DestSlot){
        
    	//1、大量检查
    	if (!IsValid(SourceSlot) || !IsValid(DestSlot)){
        
    		return false;}	
    	//1.1、最少有一个插槽在本库存
    	UArcInventoryComponent* SourceInventory = SourceSlot.ParentInventory;
    	UArcInventoryComponent* DestinationInventory = DestSlot.ParentInventory;
    	if (SourceInventory != this && DestinationInventory != this){
        
    		return false;}
    	//1.2、根据标签确定两个插槽可以Swap
    	UArcItemStack* SourceItem = SourceInventory->GetItemInSlot(SourceSlot);
    	UArcItemStack* DestItem = DestinationInventory->GetItemInSlot(DestSlot);
    	if (!DestinationInventory->AcceptsItem_AssumeEmptySlot(SourceItem, DestSlot) || !SourceInventory->AcceptsItem_AssumeEmptySlot(DestItem, SourceSlot)){
        
    		return false;}
    		
    	//2、先删后增
    	SourceInventory->RemoveItemFromInventory(SourceSlot);
    	DestinationInventory->RemoveItemFromInventory(DestSlot);
    	SourceInventory->PlaceItemIntoSlot(DestItem, SourceSlot);
    	DestinationInventory->PlaceItemIntoSlot(SourceItem, DestSlot);
    	return true;
    }

**实现:**  
检查插槽，然后交换插槽

### 1.2.4、查 ###

**作用:**  
进行状态查询以及通过Reference找到对应插槽  
共三个作用：  
查询插槽是否存在  
获取到特定插槽(物品),目前仅是单个插槽  
获取到所有库存/引用  
获取库存大小

FArcInventoryItemSlot& UArcInventoryComponent::GetItemSlot(const FArcInventoryItemSlotReference& RefSlot){
        
    	for (FArcInventoryItemSlot& SlotSlot : BagInventory.Slots){
        		
    		if (RefSlot == SlotSlot){
        
    			BagInventory.MarkItemDirty(SlotSlot);
    			return SlotSlot;}}
    	return BagInventory.Slots[0];}

**实现:**  
单个查询使用遍历+==，其他查询基本是直接输出变量

## 1.3、`ArcInventoryComponent`总结 ##

### 1.3.1 背包组件: ###

`ArcInventoryComponent`实现了基础的增删改查，满足一个背包基础的功能搭建

### 1.3.2 ArcInventory的核心 ###

`ArcInventoryComponent`为成为了系统的中心与桥梁。其主要处理的问题：

#### 1.3.2.1、数据同步 ####

贯穿增删改查的是数据同步。  
`ArcInventoryComponent`采用了针对结构体优化的`FFastArraySerializer`来储存背包数据。同时，采用更利于同步的`FArcInventoryItemSlotReference`作为Handle进行外部通讯以及RPC的工具，减轻了同步负担的同时也增加了数据安全性

#### 1.3.2.2、灵活度 ####

将背包-插槽-物品-Handle全部拆分，带来了高度的灵活性。  
**背包:**`ArcInventoryComponent`作为库存操作的整体与内外系统交互  
**插槽:**‘ArcItemSlot’:库存保存的插槽实例，并不保存实际数据，而是建立物品放入以及使用的规则  
**物品:**’ArcItemStack‘真正保存了插槽的数据，与’ArcItemSlot’通过指针连接，记录所有真正的数据，包括最大堆栈数量、物品信息等  
**Handle:**`ArcItemReference`用于作为Handle供外部调用，是外部系统获取插槽的重要途经，通过使用轻量化的Handle传输而不是直接Slot或Stack传输可以大大减轻网络的系统压力，并使外部系统更难去介入Inventory内部实现

> 以上所有类都可以通过继承实现更丰富的功能

# 二、FArcInventoryItemSlot #

继承自`FFastArraySerializerItem`，优化网络传输

## 2.1、基础属性 ##

主要是：物品/上一个物品、筛选/被筛选Tag、自身信息

UPROPERTY(BlueprintReadWrite, VisibleInstanceOnly, Category = Inventory)
    	UArcItemStack* ItemStack;
    	TWeakObjectPtr<UArcItemStack> OldItemStack;
    	
    	UPROPERTY()
    	FArcInventoryItemSlotFilterHandle ItemSlotFilter;
    	UPROPERTY(BlueprintReadWrite, VisibleInstanceOnly, Category = Inventory)
    	FGameplayTagContainer SlotTags;
    	
    	UPROPERTY(BlueprintReadOnly, VisibleInstanceOnly, Category = Inventory)
    	int32 SlotId;
    
    	UArcInventoryComponent* Owner;

### 2.1.1、`ItemStack`与`OldItemStack` ###

存储物品的现有信息和上一个信息，详情请看第二篇

### 2.1.2、`ItemSlotFilter`与`SlotTags` ###

作为筛选器以及被筛选器使用，双向筛选确定物品是否能放入当前Slot

### 2.1.3、`Owner`与`SlotId` ###

记录自身信息，方便Component获取

## 2.2、接口 ##

并没有外部需要调用的接口，仅仅用于数据检查以及网络复制

bool NetSerialize(FArchive& Ar, class UPackageMap* Map, bool& bOutSuccess);
    void PreReplicatedRemove(const struct FArcInventoryItemSlotArray& InArraySerializer);
    void PostReplicatedAdd(const struct FArcInventoryItemSlotArray& InArraySerializer);
    void PostReplicatedChange(const struct FArcInventoryItemSlotArray& InArraySerializer);
    bool operator==(FArcInventoryItemSlot const& Other) const

## 2.3、`FArcInventoryItemSlot`总结 ##

需要判断确定什么东西能进该插槽，以及确定插槽类型，将数据交给了Stack储存，实现插槽数据与控制的解耦

# 三、总结 #

`UArcInventoryComponent`、`FArcInventoryItemSlot`以及`FArcInventoryItemSlotReference`共同构成了库存的核心基础操作

## 3.1、`UArcInventoryComponent` ##

**整个库存的中枢**  
专心处理背包插槽的逻辑：增删改查，所有的操作又基于背包与物品的中间层`FArcInventoryItemSlot`，完全不需要知道物品的具体实现细节。

## 3.2、`FArcInventoryItemSlot` ##

**库存本身与物品实体之间的桥梁，库存的最小单位**  
作为插槽的具体实现，依赖于`UArcInventoryComponent`而不是实际物品，同时又与物品(‘ItemStack’)进行交互，获取自己想要的信息。

## 3.3、`FArcInventoryItemSlotReference` ##

**库存与外界实体交互的桥梁**  
其可以看作是一个插槽的Handle，记录插槽的引用信息供内外部调用。方便使用、将内部实现与外部接口进行了隔离，方便数据传输以及RPC调用。

[https_www.unrealengine.com_marketplace_zh-CN_product_arc-inventory]: https://www.unrealengine.com/marketplace/zh-CN/product/arc-inventory
[https_redirect.epicgames.com_redirectTo_https_punyhumangames.github.io_ArcPluginsDocumentation_arcinventory]: https://redirect.epicgames.com/?redirectTo=https://punyhumangames.github.io/ArcPluginsDocumentation/arcinventory/
[https_docs.unrealengine.com_4.27_en-US_API_Runtime_Engine_Engine_FFastArraySerializer]: https://docs.unrealengine.com/4.27/en-US/API/Runtime/Engine/Engine/FFastArraySerializer/
[https_ikrima.dev_ue4guide_networking_network-replication_fast-tarray-replication]: https://ikrima.dev/ue4guide/networking/network-replication/fast-tarray-replication/