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10 — Serialization

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The plugin has no save system of its own — deliberately. Every project's is different, and a plugin that imposes its own slot format usually ends up being worked around.

Instead, the inventory hands you a plain struct that you put into your own USaveGame.

What it looks like

UCLASS()
class UMySaveGame : public USaveGame
{
    GENERATED_BODY()

public:
    UPROPERTY(SaveGame)
    FISInventorySaveData Backpack;

    UPROPERTY(SaveGame)
    FISEquipmentSaveData Loadout;
};

Saving:

UMySaveGame* Save = Cast<UMySaveGame>(
    UGameplayStatics::CreateSaveGameObject(UMySaveGame::StaticClass()));

Save->Backpack = InventoryComponent->ExportState();
Save->Loadout  = EquipmentComponent->ExportState();

UGameplayStatics::SaveGameToSlot(Save, TEXT("Slot1"), 0);

Loading:

if (UMySaveGame* Save = Cast<UMySaveGame>(
        UGameplayStatics::LoadGameFromSlot(TEXT("Slot1"), 0)))
{
    InventoryComponent->ImportState(Save->Backpack);
    EquipmentComponent->ImportState(Save->Loadout);
}

In Blueprint it's all the same: Export State / Import State are ordinary nodes.

What exactly is saved

Data How it's stored
Item type FSoftObjectPath — a path to the asset, not a pointer
Slot number the exact index, so the layout doesn't shift
Stack size as is
Instance state durability, charges, quality — everything from StatValues
Slot count so an upgraded backpack loads upgraded
Weight limit for the same reason

A path instead of a pointer is what lets a save survive a game restart, a patch, and even an asset move (Unreal redirectors are honoured).

Item state really is saved

This is not "remember the type and count":

Sword at 12/100 durability  →  saved  →  loaded  →  sword at 12/100 durability

On load the creation hooks are not run — otherwise a rusty sword would come back from the workshop brand-new. StatValues are assigned directly, as restored facts, not as changes.

When to call ImportState

Only after the owning actor is fully initialised. From the constructor is too early.

In practice: BeginPlay, or the moment your save system is ready to apply the data.

ImportState clears the current contents itself before restoring — no need to clear beforehand.

What happens if an item no longer exists

The game updated, the asset was deleted, and the player was carrying it.

Such an item is skipped with a warning in the log, and the rest loads normally. One removed item never costs the player the whole save.

ImportState returns false to signal that not everything was restored — this is information, not an error. Whether to show anything to the player is up to you.

Equipment: two differences

Items are placed straight into slots, without going through the inventory. This is deliberate: restoring equipment shouldn't depend on whether there's room in the backpack.

Slots the character no longer has (the body plan changed between versions) are skipped with a warning.

The order when loading both components:

InventoryComponent->ImportState(Save->Backpack);
EquipmentComponent->ImportState(Save->Loadout);

On restore, equipment first clears the current loadout without returning it to the inventory — otherwise the backpack would gain copies of things the save already accounts for separately.

Multiplayer

Both functions are server-only. A call on a client is ignored with a warning.

This is correct: the inventory is authoritative on the server, so it's restored there, and clients get the result through ordinary replication.

If your game saves progress separately per player, call ImportState on the server for the appropriate PlayerState (or pawn — depending on where you placed the component).

What is NOT saved

Not saved Why, and what to do
Items on the ground (AISItemPickup) These are level actors. Save them with your own world-save system, or don't save them at all.
Chest state The same — they're actors. Call ExportState on ContainerInventory if you need it.
Consumable cooldowns Deliberately ephemeral; after loading the item is available right away.
Equipment visual actors Recreated from the fragment when the slot is restored.

Saving a chest isn't hard — its inventory is the same:

Save->ChestContents = Container->GetContainerInventory()->ExportState();

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