12 — API Reference
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The full public API. Expanded explanations with examples are in the tooltips
right in the editor: hover over any field or node.
Nearly everything listed here is callable from both Blueprint and C++. The
exceptions are marked (C++ only) and there are just two: GetEntriesView on
both containers, which returns an array without a copy, and the
IISInventoryInterface interface. They add no capability to the plugin —
both have Blueprint equivalents (GetAllEntries and component lookup via
UISInventoryBlueprintLibrary).
UISInventoryBlueprintLibrary — shortcuts
The shortest path to common actions. These functions find the component
themselves, so you don't need to look it up by hand.
| Function |
Description |
GetInventoryFor(Actor) |
find the inventory — on the actor, its PlayerState or pawn |
GetEquipmentFor(Actor) |
the same for equipment |
HasInventory(Actor) |
whether there's an inventory at all |
GiveItemTo(Actor, Def, Count) |
grant; returns how many actually fit |
TakeItemFrom(Actor, Def, Count, bAllowPartial) |
take; "all or nothing" by default |
GetItemCountFor(Actor, Def) |
how many it has |
HasItemCount(Actor, Def, Count) |
whether it has enough |
MoveItemBetweenActors(From, To, Slot) |
move in the right direction |
GetItemsWithTag(Actor, Tag) |
every item with a tag |
GetCarriedWeight(Actor) |
total weight |
GetItemDisplayText(Instance) |
"Sword" or "Arrow x12" |
GetUseResultText(Result) |
text for the use result |
UISInventoryComponent
Configuration
| Field |
Description |
MaxSlots |
number of slots; 0 = unlimited. Replicated |
MaxWeight |
weight limit; 0 = weight is ignored. Replicated |
AllowedItemTags |
if set — only items with one of these tags are accepted |
BlockedItemTags |
items with these tags are refused (checked first) |
SlotRestrictions |
rules for slot ranges |
StartingItems |
items granted at startup (on the server) |
Actions — callable from anywhere
| Method |
Description |
TryAddItem(Def, Count, OutRemainder) |
add copies; OutRemainder is how many didn't fit |
TryAddItemInstance(Instance, PreferredSlot) |
add an existing object preserving its state (server) |
TryRemoveItemFromSlot(Slot, Count) |
remove from a specific slot |
TryRemoveItem(Def, Count, OutRemainder) |
remove by type, spanning several stacks |
TryTransferTo(Target, FromSlot, ToSlot, Count) |
give to another inventory |
TryTransferFrom(Source, FromSlot, ToSlot, Count) |
take from another inventory |
TryCollect(Collectible) |
pick an item up from the world — call on the player's inventory, not the pickup |
TryQuickMoveTo(Target, FromSlot) |
"shift-click": the target picks the spot |
TrySplitStack(Slot, SplitCount) |
split a stack |
TrySwapSlots(A, B) |
swap places or merge |
TryMoveToSlot(From, To) |
the same, in other words |
TryUseItem(Slot, Instigator) |
use; returns EISItemUseResult |
TryClearInventory() |
empty it |
SortInventory(Mode) |
sort and compact from slot 0 |
CompactStacks() |
merge partial stacks without rearranging the rest |
Queries — safe on a client
| Method |
Description |
GetItemAtSlot(Slot) |
the item in the slot, or null |
GetItemCount(Def) |
how many copies in total |
HasItem(Def, Count) |
whether there are at least that many |
GetAllItems() |
every item |
GetAllEntries() |
every occupied slot with its index |
GetEntriesView() |
the same, without an array copy (C++ only) |
FindItemSlot(Def) |
the first slot with this type |
FindAllItemSlots(Def) |
every slot with this type |
FindSlotOfInstance(Instance) |
where exactly this object is |
GetTotalItemCount() |
the sum of all stacks |
GetOccupiedSlotCount() / GetFreeSlotCount() |
occupied / free |
GetCurrentWeight() |
current weight |
IsFull() / IsEmpty() |
state |
IsValidSlot(Slot) / IsSlotOccupied(Slot) |
slot checks |
CanAcceptItem(Def) |
whether this type is accepted at all |
CanAcceptItemCount(Def, Desired) |
how many will actually fit right now |
CanSlotAcceptItem(Slot, Def) |
whether a specific slot will accept it |
HasContainerAuthority() |
whether this side has authority (shared by inventory and equipment) |
CanAcceptRequestFrom(Requester) |
whether this actor is allowed to change the container |
Serialization
ExportState() → FISInventorySaveData · ImportState(State) (server)
Events
| Event |
When |
OnInventoryChanged |
any change (with the change type) |
OnItemAdded |
a slot received an item |
OnItemRemoved |
a slot emptied |
OnItemChanged |
the item is the same, the data changed |
OnAddRejected |
an add was refused, with the reason text |
UISEquipmentComponent
Configuration
| Field |
Description |
AvailableSlots |
the body plan — which slots exist at all |
LinkedInventory |
the backpack items are taken from and returned to |
bAutoLinkInventoryOnSameActor |
find the inventory on the same actor (on by default) |
Actions
| Method |
Description |
TryEquipFromInventorySlot(Index) |
equip whatever is in an inventory slot |
TryEquipItem(Item, Slot, bRemoveFromInventory) |
equip a specific item |
TryUnequipSlot(Slot, bReturnToInventory) |
unequip |
TrySwapSlots(A, B) |
swap places (requires AlternativeSlots on the items) |
TryUnequipAll(bReturnToInventory) |
unequip everything |
TryUseEquippedItem(Slot, Instigator) |
use a worn item |
Queries
| Method |
Description |
GetEquippedItem(Slot) |
the item in the slot, or null |
GetEquippedActor(Slot) |
the slot's visual actor |
IsSlotEquipped(Slot) / HasSlot(Slot) |
state and slot presence |
GetAllEquippedItems() / GetOccupiedSlots() / GetAllEntries() |
iteration |
GetEntriesView() |
iteration without an array copy (C++ only) |
CanEquipToSlot(Item, Slot) |
whether it can be equipped here |
GetDesiredSlotForItem(Item) |
where the item asks to go |
GetTotalStatValue(StatTag) |
the aggregate stat across everything worn |
GetLinkedInventory() |
the linked backpack; if the cache is empty — looks on the actor |
HasContainerAuthority() |
whether this side has authority (shared by inventory and equipment) |
Serialization and events
ExportState() / ImportState(State)
| Event |
When |
OnItemEquipped |
a slot became occupied — the equip itself, not any change |
OnItemUnequipped |
a slot freed up |
OnEquippedItemChanged |
the item is the same, its data changed (durability, charges) |
OnEquipmentActorSpawned |
the slot's visual actor was created and attached |
The first three events are exactly the same trio as the inventory's
(OnItemAdded / OnItemRemoved / OnItemChanged). Bind the equip sound to
OnItemEquipped: it won't fire again just because the sword lost a point of
durability.
UISItemDefinition — the item type
| Field / method |
Description |
DisplayName, Description, Icon, PickupMesh |
presentation |
ItemTags |
classification |
Fragments |
capabilities |
FindFragmentByClass / HasFragment / GetAllFragments |
fragment access |
HasAnyTags / HasAllTags |
tag checks |
GetMaxStackSize() |
the stack size (chained through the fragments) |
GetUnitWeight() |
the unit weight |
IsUsable() |
whether "use" makes sense |
UISItemInstance — a concrete copy
| Field / method |
Description |
Definition, StackCount, StatValues |
state |
GetStatValue / SetStatValue / ModifyStatValue |
stats |
HasStat / ClearStatValue |
presence and removal |
CanStackWith(Other) |
whether it can merge |
GetMaxStackSize / IsStackFull / GetAvailableStackSpace |
stack |
GetDisplayName / GetDescription |
presentation |
GetStackWeight() / IsUsable() |
derived |
DuplicateInstance(Outer) |
a copy preserving state |
GetOwningContainer() |
who holds it — the inventory or equipment |
GetOwningInventory() |
the inventory, if it's that; null when the item is worn |
ConsumeFromContainer(Count) |
ask whoever holds it to spend copies |
Fragments — their own helpers
Each fragment's fields are described in 04 — Fragments.
Besides fields, some fragments expose functions you can call directly:
| Fragment |
Function |
Description |
UISFragment_Durability |
GetCurrentDurability(Instance) |
the copy's current durability |
|
GetDurabilityPercent(Instance) |
0–1, ready for a progress bar |
|
IsBroken(Instance) |
whether durability dropped to zero |
|
Repair(Instance, Amount) |
repair; a negative value — fully (server) |
UISFragment_Consumable |
GetRemainingCharges(Instance) |
how many charges are left |
UISFragment_Equippable |
AcceptsSlot(Slot) |
whether the item agrees to live in this slot |
All twelve hooks a custom fragment overrides are also public API:
OnInstanceCreated, OnAddedToInventory, OnRemovedFromInventory,
CanBeAddedTo, CanStackWith, CanBeUsed, IsUsable, OnUsed, OnEquipped,
OnUnequipped, ModifyMaxStackSize, ModifyUnitWeight.
UISInventoryQueryLibrary — searching by description
For when the question is more complex than "how many of these do I have": "all
the weapons that are worn down", "everything sellable", "the first arrow stack
with more than ten".
| Function |
Description |
QueryInventory(Inv, Query) |
every matching item |
QueryInventoryFirst(Inv, Query) |
the first match, or null |
QueryInventoryCount(Inv, Query) |
the total copy count across all matches |
QueryInventorySlots(Inv, Query) |
the slot indices of all matches, ascending |
MakeTagQuery(Tag) |
shortcut: everything with one tag |
MakeDefinitionQuery(Def) |
shortcut: exactly one item type |
FISInventoryQuery fields (an empty query matches everything; fields combine
with AND):
| Field |
Description |
RequiredTags |
the item must carry all of these tags |
AnyOfTags |
the item must carry at least one of these tags |
ExcludedTags |
an item with any of these tags is excluded |
RequiredFragment |
the item must have a fragment of this class (subclasses too) |
MinStackCount / MaxStackCount |
stack-size bounds |
SpecificDefinition |
exactly this item type |
Interfaces — integration points
| Interface |
For |
IISCollectibleInterface |
make your own actor something UISInventoryComponent::TryCollect can pick up. AISItemPickup already implements it; your own — only if your "collectible" object isn't a subclass of it. One method: TryGiveContents(Collector), called already on the server |
IISInventoryInterface |
say which of several inventories on an actor is primary — GetInventoryComponent, GetEquipmentComponent, GetAllInventoryComponents. Rarely needed: GetInventoryFor finds the single one itself. (C++ only) |
World objects (InventorySystemWorld)
AISLootContainer
| Member |
Description |
ContainerInventory |
the contents |
LootTable, bGenerateLootOnSpawn |
filling |
bUseWeightedLoot, WeightedDropCount |
"exactly N items" mode |
bSingleUse |
a one-time chest |
Open(Opener) / Close(Closer) |
interaction — server-only, don't forward themselves |
CanOpen() / IsEmpty() |
state |
ResetContainer(bClear) |
allow it to refill |
BP_OnOpened / BP_OnClosed / BP_OnLooted / BP_OnLootGenerated |
visual hooks |
AISItemPickup
| Member |
Description |
ItemDefinition, ItemCount |
contents for level-placed pickups |
HeldItem |
the real object with state |
bDestroyOnCollected, LifeSpanSeconds |
behaviour |
TryCollect(Collector) |
pick up — server-only; from a client call UISInventoryComponent::TryCollect |
HasContents() / GetPickupText() |
state and label |
SpawnForItem(World, Item, Location, Class) |
drop an existing item into the world (server) |
Which TryCollect to call. The one on the player's inventory. The pickup
has no network connection, so it can't forward the request to the server
itself — the player's inventory can. This is the same reason you take from a
container through TryTransferFrom rather than the container's own methods.
UISLootTable
| Method |
Description |
GenerateLoot() |
roll each entry separately by DropChance |
GenerateWeightedLoot(Count) |
exactly N entries by Weight |
PopulateInventory(Inv, bWeighted, Count) |
generate and place immediately |
UISInventoryWorldSubsystem — world-level state
Everything shared for the game but not for the process: subscriptions and
timers that must disappear with the world. Get it via
UISInventoryWorldSubsystem::Get(WorldContext).
| Member |
Description |
GetPlayerInventory(PlayerState) |
find a player's inventory, whether on the PlayerState or the pawn |
GetPlayerEquipment(PlayerState) |
the same for equipment |
OnConsumableUsed |
the consumable-used event — the item, who used it, EffectTags |
GetFragmentCooldownRemaining(Fragment) |
how many seconds are left on a fragment's shared cooldown |
StartFragmentCooldown(Fragment, Seconds) |
start it |
Why not a static on the fragment class: the fragment is shared by the whole
game, and a static on it would be shared by every world in the process too.
In PIE the server and client worlds would hear each other's uses, and
subscriptions from a previous session would stay alive into the next.
The cooldown is keyed by fragment, so it's one per world for every player.
This is a deliberately simple tool — build per-player cooldowns on top of
OnConsumableUsed.
Debugging (InventorySystemDebug)
| Function |
Description |
ToggleInventoryDebugOverlay(PC) |
open / close the inspector |
IsInventoryDebugOverlayOpen(PC) |
whether it's open now |
Both do nothing in Shipping. Console commands —
13 — Debugging.
Enums
| Type |
Values |
EISItemUseResult |
Success, NoItem, NotUsable, Blocked |
EISInventoryChangeType |
ItemAdded, ItemRemoved, ItemChanged, SlotSwapped |
EISSortMode |
ByName, ByStackCount, ByType, ByWeight |
EISInventoryHost |
PlayerState, Pawn |
Structs
| Type |
Description |
FISItemStatEntry |
one per-instance value: tag + number |
FISSlotRestriction |
a rule for a slot range |
FISInventoryEntry |
an occupied slot: index + item |
FISEquipmentEntry |
an occupied equipment slot: tag + item + actor |
FISLootTableEntry |
a loot-table entry: item, count range, chance and weight |
FISLootDrop |
a roll result: item + exact count |
FISInventoryQuery |
a description of what to search an inventory for |
FISItemSaveData / FISInventorySaveData / FISEquipmentSaveData |
serialization |
Project settings
UISInventorySettings — Project Settings → Game → Inventory System.
Everything is off or neutral by default; details in
02 — Setup.
| Field |
Description |
bAutoCreatePlayerInventory |
give every player an inventory automatically |
bAutoCreatePlayerEquipment |
and equipment along with it |
AutoInventoryHost |
where it lives: PlayerState (survives death) or Pawn |
DefaultInventorySlots |
how many slots an automatic inventory gets |
DefaultEquipmentSlots |
the body plan for automatic equipment |
InventoryComponentClass / EquipmentComponentClass |
your subclasses instead of the defaults |
MaxInteractionDistance |
server-side distance limit for requests; 0 — don't check |
bValidateItemsOnStartup |
validate item assets at editor startup |
bVerboseLogging |
detailed log of every inventory change |