ue4 FFastArraySerializer and FFastArraySerializerItem

USTRUCT(BlueprintType)
struct INVENTORYSYSTEM_API FInventoryItem : public FFastArraySerializerItem
{

	GENERATED_USTRUCT_BODY()

public:

	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = "FInventoryItem")
		int32 Amount;

	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = "FInventoryItem")
		int32 MaxAmount;

	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = "FInventoryItem")
		bool bCanStack = false;

	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = "FInventoryItem")
		UInventoryItemAsset* ItemAsset = nullptr;

	// Item property key value pairs for dynamic properties
	UPROPERTY(BlueprintReadWrite, EditAnywhere, Category = "Inventory System", DisplayName = "Dynamic Item Properties")
		FItemPropertyArray ItemProperties;

	void PreReplicatedRemove(const struct FInventoryArray& InArraySerializer);
	void PostReplicatedAdd(const struct FInventoryArray& InArraySerializer);
	void PostReplicatedChange(const struct FInventoryArray& InArraySerializer);

	FInventoryItem();

	FInventoryItem(int32 NewAmount, int32 NewMaxAmount, bool bNewCanStack, UInventoryItemAsset* NewItemAsset);

	friend bool operator== (const FInventoryItem& First, const FInventoryItem& Other)
	{
		return (First.ItemAsset == Other.ItemAsset && First.ItemProperties.Properties == Other.ItemProperties.Properties);
	}

	friend bool operator!= (const FInventoryItem& First, const FInventoryItem& Other)
	{
		return (First.ItemAsset != Other.ItemAsset || First.ItemProperties.Properties != Other.ItemProperties.Properties);
	}

	friend bool operator>= (const FInventoryItem& First, const FInventoryItem& Other)
	{
		return (First.Amount >= Other.Amount);
	}

	friend bool operator<= (const FInventoryItem& First, const FInventoryItem& Other)
	{
		return (First.Amount <= Other.Amount);
	}

	friend bool operator> (const FInventoryItem& First, const FInventoryItem& Other)
	{
		return (First.Amount > Other.Amount);
	}

	friend bool operator< (const FInventoryItem& First, const FInventoryItem& Other)
	{
		return (First.Amount < Other.Amount);
	}
};


USTRUCT(BlueprintType)
struct FInventoryArray : public FFastArraySerializer
{
	GENERATED_USTRUCT_BODY()

	UPROPERTY(BlueprintReadWrite, EditAnywhere)
		TArray< FInventoryItem > Items;

	bool NetDeltaSerialize(FNetDeltaSerializeInfo & DeltaParms);

	FInventoryArrayChangedDelegate InventoryArrayChangedDelegate;
};

    template<>
struct TStructOpsTypeTraits< FInventoryArray > : public TStructOpsTypeTraitsBase2< FInventoryArray >
{
	enum
	{
		WithNetDeltaSerializer = true,
	};
};