InventorySystem User Guide¶

A data-driven inventory and equipment system for Unreal Engine 5.7 with full multiplayer support.

Items are authored as Data Assets, gameplay code calls a single method, and the plugin does the rest — including network replication.

Version 1.0 · Runtime · UE 5.7 · Release Notes

Quick start¶

1. Enable the plugin. Copy Plugins/InventorySystem into your project's Plugins/ folder and enable it: Edit → Plugins → Inventory System.

2. Create an item. Content Browser → right-click → Miscellaneous → Data Asset → ISItemDefinition. Name it DA_HealthPotion, set DisplayName, and in the Fragments field add:

Stackable → MaxStackSize = 10
Consumable → ConsumeAmount = 1

Don't want to author anything just to look around? The plugin ships seven ready-made items under InventorySystem Content → Demo → Items (turn on Show Plugin Content in the Content Browser settings to see them). A sword, shield, helmet, torch, potion, ore and relic — together they cover all five fragments.

3. Give a character an inventory. Character Blueprint → Add Component → Inventory.

4. Try it. Press Play and open the console:

InvGive Potion 5      give yourself 5 potions
InvOverlay            open the inspector

Done — items are granted, stacked and used.

The same from code:

int32 Remainder = 0;
InventoryComponent->TryAddItem(PotionDefinition, 5, Remainder);

That line works both in single-player and on a multiplayer client — with no HasAuthority() branch on your side.

The three ideas the plugin rests on¶

If you read only one paragraph, read this one.

1. An item is a set of fragments, not a class. There is no Weapon or Potion base class. A sword is Equippable + Durability, a potion is Stackable + Consumable, a torch is all three at once: Equippable + Durability + Consumable (held in hand, has a fuel reserve, spent on use). "All three" means three of the four types just mentioned, not every fragment in the plugin: there are five in total (Stackable, Equippable, Consumable, Durability, Weight). Adding a capability = adding a fragment; the inventory code doesn't change.

2. One API for any game mode. Every method that changes state is named Try* and is callable from anywhere. In single-player it runs in place and creates no RPC at all; on a client it forwards itself to the server.

3. What makes a copy unique lives in the instance. A sword at 12/100 durability and a fresh sword reference the same asset but hold different per-instance values — which is exactly why they don't merge into a stack.

Who should read what¶

You	Start with
Total beginner — want to see a result in 10 min, not read chapter by chapter	From asset to a player's hand
Designer authoring items	01 → 03 → 04
Gameplay programmer	05 → 11
Reading the code / extending the plugin	Architecture → 04
UI programmer	08 → 12
Multiplayer programmer	01 → 09
QA / tooling	13

Something behaving oddly? 14 — FAQ has a "why isn't it working" checklist.

Chapters¶

#	Chapter	What's inside
–	From asset to a player's hand	A 10-minute story: a sword, a torch and a potion from Data Asset to the player's hand
–	Release Notes	What's here, what changed, what's not there yet
01	Core Concepts	Type and instance, fragments, stacking rules, sparse slots
02	Setup	Installation, Project Settings, where the inventory lives and how to find it
03	Authoring Items	Field reference and ready recipes: potion, sword, ore, ammo
04	Fragments	The five shipped fragments, every hook, how to write your own
05	Inventory Operations	Add, move, use, sort; filters, weight, events
06	Equipment	Slots as tags, equipping, visual actors, aggregate stats
07	Loot and world items	Loot tables, chests, items on the ground, a custom container
08	Building the UI	Grid, icons, tooltips, drag-and-drop, a chest window
09	Multiplayer	Why the same code works in both modes; the one exception
10	Serialization	`ExportState` / `ImportState`, embedding into your save game
11	Recipes	Crafting, trading, a hotbar, looting a corpse, dropping, repair
12	API Reference	The full public API
13	Debugging	Inspector, console commands, logs, a problem checklist
14	FAQ	Short answers to common questions
–	Architecture	How the plugin is built internally, and why

Conventions¶

"Item type" is a UISItemDefinition asset. "Instance" is a concrete copy in someone's inventory (UISItemInstance).
Code snippets are C++ unless noted otherwise. Nearly every function shown is also callable from Blueprint; the two exceptions are marked (C++ only) in 12 — API Reference and add no capability.
"Inventory" means UISInventoryComponent, "equipment" means UISEquipmentComponent.