Storage Unit
Introduction
The Smart Storage Unit (SSU) is a programmable, on-chain storage structure. Players can store, withdraw, and manage items and the owner can define custom rules through extension contracts.
Design
A storage unit has two types of inventories:
Primary inventory — owned by the storage unit owner, accessed via the storage unit's
OwnerCap. This is the main inventory for the owner's items.Ephemeral inventories — temporary, per-character inventories for players other than the owner. Used for trading, deposits, etc. Ephemeral inventories have a smaller capacity than the primary inventory to prevent abuse of the owner's storage unit.
Ephemeral inventories are created on-demand and stored as dynamic fields keyed by the character's OwnerCap ID. Each ephemeral inventory is accessed by the interacting character's own OwnerCap, like biometric authentication for temporary access. This avoids minting separate OwnerCaps just for ephemeral inventory access.
Items in inventories are on-chain representations of in-game resources.
Interacting with a Storage Unit
1. Bridging Items (Game to Chain)
For any on-chain interaction, items must first be available on-chain. Players move items from in-game into the chain, and can move them back out to the game.
Game → Chain — items are minted on-chain from in-game data.
Chain → Game — on-chain items are burned and returned to the game.
2. Owner Deposit & Withdraw
Once items are on-chain, the owner can deposit and withdraw directly using their owner capability. The owner signs the transaction and proves access with their OwnerCap; They can perform these actions from a dApp.
3. Custom Logic via Extensions
The owner can deploy custom rules (a Move contract) and register it as the storage unit’s extension. After that, the extension controls how items are deposited or withdrawn — for example:
Vending machine — players pay (e.g. in tokens) and receive an item from the unit.
Trade hub — custom rules for listing, buying, and exchanging items.
Gated access — only characters that meet certain conditions can deposit or withdraw.
Extension-to-owned — the extension can deposit items into a specific player’s owned inventory (e.g. async delivery, guild hangars, rewards); the recipient does not need to be the transaction sender.
The extension uses the same pattern as the Gate: the owner authorizes a contract type on the storage unit, and that contract’s logic runs when players interact. For API details and build steps, see the Storage Unit Build Guide.
Next Steps
Build a custom storage unit extension: Build Guide
Reference:
world-contracts — EVE Frontier Sui Move contracts
storage_unit.move — core storage unit module
inventory.move — inventory primitives
contracts/world — world contract package
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