Object Permissions

Summary

• ObjectRefs are permissions for object management in Move
• Three types: ExtendRef, TransferRef, and DeleteRef
• ExtendRef allows signer generation after object creation
• TransferRef enables object transfer without owner's signer
• DeleteRef is used for object deletion
• ObjectRefs are generated from ConstructorRef during object creation
• Practical example demonstrates generating and storing refs
• Understanding ObjectRefs is crucial for effective object management in Move

Understanding ObjectRefs in Move

In this tutorial, we'll explore ObjectRefs, which are crucial for managing objects in Move. We'll cover three types of ObjectRefs and their uses.

What are ObjectRefs?

ObjectRefs are permissions or capabilities for object management, generated from ConstructorRef during object creation. They're different from Object references.

Types of ObjectRefs

• ExtendRef: Allows signer generation after object creation.
  • Can be stored for future use
  • Offers more flexibility than ConstructorRef
• TransferRef: Enables object transfer without owner's signer.
  • Can transfer object to a different address
  • Can 'freeze' an object, preventing further transfers
• DeleteRef: Used for object deletion.
  • Can be stored
  • One-time use capability

Practical Application

In the next section, we'll walk through a step-by-step example of generating and storing these refs. This hands-on approach will help solidify your understanding of ObjectRefs and their practical uses in Move programming.

use aptos_framework::object::{Self, Object, ExtendRef, DeleteRef, TransferRef};

const MOVEMENT_OBJECT_NAME: vector<u8> = b"MovementObjectName";

#[resource_group_member(group = aptos_framework::object::ObjectGroup)]
struct MovementObject has key {
    value: u64,
    extend_ref: ExtendRef,
    transfer_ref: TransferRef,
    delete_ref: DeleteRef
}

fun init_module(owner: &signer) {
    let state_object_constructor_ref = &object::create_named_object(owner, MOVEMENT_OBJECT_NAME);
    let state_object_signer = &object::generate_signer(state_object_constructor_ref);
    move_to(state_object_signer, MovementObject {
        value: 10,
        extend_ref: object::generate_extend_ref(state_object_constructor_ref),
        transfer_ref: object::generate_transfer_ref(state_object_constructor_ref),
        delete_ref: object::generate_delete_ref(state_object_constructor_ref)
    });
}