第一次提交

Plugins/GIS/Source/GenericInventorySystem/Private/Drops/GIS_RandomItemDropperComponent.cpp

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+// Copyright 2025 https://yuewu.dev/en  All Rights Reserved.
+
+
+#include "Drops/GIS_RandomItemDropperComponent.h"
+#include "GameFramework/Actor.h"
+#include "GIS_InventorySystemComponent.h"
+#include "GIS_ItemCollection.h"
+#include "GIS_LogChannels.h"
+
+#include UE_INLINE_GENERATED_CPP_BY_NAME(GIS_RandomItemDropperComponent)
+
+TArray<FGIS_ItemInfo> UGIS_RandomItemDropperComponent::GetItemsToDropInternal() const
+{
+	TArray<FGIS_ItemInfo> Results;
+
+	UGIS_InventorySystemComponent* Inventory = UGIS_InventorySystemComponent::FindInventorySystemComponent(GetOwner());
+	if (Inventory == nullptr)
+	{
+		GIS_CLOG(Error, "requires inventory system component to drop items.")
+		return Results;
+	}
+	UGIS_ItemCollection* Collection = Inventory->GetCollectionByTag(CollectionTag);
+	if (Collection == nullptr)
+	{
+		GIS_CLOG(Error, " inventory missing collection with tag:%s'", *CollectionTag.ToString())
+		return Results;
+	}
+
+	const TArray<FGIS_ItemStack>& ItemStacks = Collection->GetAllItemStacks();
+
+	TArray<FGIS_ItemInfo> ItemInfos;
+	ItemInfos.Reserve(ItemStacks.Num());
+	int32 ProbabilitySum = 0;
+
+	for (int32 i = 0; i < ItemStacks.Num(); ++i)
+	{
+		//加权
+		ProbabilitySum += ItemStacks[i].Amount;
+		ItemInfos[i] = FGIS_ItemInfo(ProbabilitySum, ItemStacks[i]);
+	}
+
+	int32 RandomAmount = FMath::RandRange(MinAmount, MaxAmount + 1);
+	Results.Empty();
+
+	for (int i = 0; i < RandomAmount; i++)
+	{
+		auto& selectedItemInfo = GetRandomItemInfo(ItemInfos, ProbabilitySum);
+		bool foundMatch = false;
+		//去重，多个栈可能指向同一个道具实例，若发现重复
+		for (int j = 0; j < Results.Num(); j++)
+		{
+			if (Results[j].Item == selectedItemInfo.Item)
+			{
+				Results[j] = FGIS_ItemInfo(Results[j].Amount + 1, Results[j]);
+				foundMatch = true;
+				break;
+			}
+		}
+
+		if (!foundMatch) { Results.Add(FGIS_ItemInfo(1, selectedItemInfo)); }
+	}
+
+	return Results;
+}
+
+const FGIS_ItemInfo& UGIS_RandomItemDropperComponent::GetRandomItemInfo(const TArray<FGIS_ItemInfo>& ItemInfos, int32 ProbabilitySum) const
+{
+	int32 RandomProbabilityIdx = FMath::RandRange(0, ProbabilitySum);
+
+	int32 min = 0;
+	int32 max = ItemInfos.Num() - 1;
+	int32 mid = 0;
+
+	while (min <= max)
+	{
+		mid = (min + max) / 2;
+		if (ItemInfos[mid].Amount == RandomProbabilityIdx)
+		{
+			++mid;
+			break;
+		}
+
+		if (RandomProbabilityIdx < ItemInfos[mid].Amount
+			&& (mid == 0 || RandomProbabilityIdx > ItemInfos[mid - 1].Amount)) { break; }
+
+		if (RandomProbabilityIdx < ItemInfos[mid].Amount) { max = mid - 1; }
+		else
+		{
+			min = mid + 1;
+		}
+	}
+
+	return ItemInfos[mid];
+}