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Design Pattern: Autonomous Objects

Overview

Demonstrates two fundamental design patterns for working with Aptos Objects:

  1. Autonomous Object Pattern: Creating an object at module deployment that can generate its own signer for programmatic actions without requiring the deployer to sign every transaction.
  2. Object Ownership Permission Pattern: Ensuring only the owner of an object can perform privileged operations on it.

Difficulty

Intermediate

Concepts Demonstrated

  • Named objects: object::create_named_object for deterministic, non-deletable object addresses
  • ExtendRef: Stored at creation time; used later to generate a signer via generate_signer_for_extending
  • TransferRef: Controls whether an object can be transferred; supports soulbound (non-transferable) objects
  • DeleteRef: Controls whether an object can be deleted; named and sticky objects cannot be deleted
  • init_module: Runs once at contract deployment to set up the autonomous object
  • Ownership checks: object::is_owner (direct owner) vs object::owns (recursive ownership check)

Key Structs

Struct Purpose
ObjectRefs Stores ExtendRef, optional TransferRef, and optional DeleteRef for controlling the object

Key Functions

Function Visibility Description
init_module private Creates the autonomous object on deployment
fetch_object_address public Returns the deterministic address of the object
get_object_signer public Returns the object's signer after verifying the caller is the owner

Design Patterns Explained

Autonomous Object Pattern

// At deployment: create a named object and store its ExtendRef
let constructor_ref = object::create_named_object(deployer, OBJECT_SEED);
let extend_ref = object::generate_extend_ref(&constructor_ref);

// Later: generate a signer from the stored ExtendRef
let object_signer = object::generate_signer_for_extending(&extend_ref);
// The object_signer can now perform actions (transfer assets, create sub-objects, etc.)

Object Ownership Permission Pattern

// Check that only the owner can get the signer
let caller_address = signer::address_of(caller);
let object = object::address_to_object<ObjectRefs>(object_address);
assert!(caller_address == object::owner(object), E_NOT_OBJECT_OWNER);

Deploy & Run
Package snippets/design-patterns/autonomous-objects
Named address deploy_address

Deploy

aptos move publish --named-addresses deploy_address=default --package-dir snippets/design-patterns/autonomous-objects

Related Examples