Account Operations

The #[component] macro automatically provides methods on self for interacting with the current account during a transaction. Read-only queries are available on &self, and mutations (add/remove assets, increment nonce) require &mut self.

Read-only queries (&self)

#[component]
impl MyAccount for MyAccountStorage {
    fn check_state(&self, asset_id: Word) {
        // Account identity
        let id: AccountId = self.get_id();
        let nonce: Nonce = self.get_nonce();

        // Vault queries
        let value: Word = self.get_asset(asset_id);
        let initial_value: Word = native_account::get_initial_asset(asset_id);
        let has_asset: bool = self.has_asset(asset_id);
        let root: Word = self.get_vault_root();
        let initial_root: Word = native_account::get_initial_vault_root();

        // Commitment queries
        let commitment: Word = self.compute_commitment();
        let initial_commit: Word = native_account::get_initial_commitment();
        let storage: Word = self.compute_storage_commitment();
        let initial_storage: Word = native_account::get_initial_storage_commitment();
        let code: Word = self.get_code_commitment();

        // Procedure queries
        let count: u32 = self.get_num_procedures();
        let proc_root: Word = self.get_procedure_root(0);
        let exists: bool = self.has_procedure(proc_root);
    }
}

Mutations (&mut self)

#[component]
impl MyAccount for MyAccountStorage {
    fn receive_asset(&mut self, asset: Asset) {
        // Add an asset to the vault — returns the resulting value word
        let stored_value: Word = self.add_asset(asset);
    }

    fn send_asset(&mut self, asset: Asset, note_idx: NoteIdx) {
        // Remove an asset from the vault — returns the resulting value word
        // Proof generation fails if the asset doesn't exist or insufficient balance
        self.remove_asset(asset);
        output_note::add_asset(asset, note_idx);
    }
}

The nonce must be incremented for any transaction that modifies account state. Without it, the same transaction could be replayed.

When proof generation fails

Several operations cause proof generation to fail if preconditions aren't met:

Operation	Fails when
remove_asset(asset)	Asset not in vault or insufficient balance
get_procedure_root(index)	Index out of bounds
Any assert!()	Condition is false
Transaction body (overall)	No state change occurred and no notes were consumed

When proof generation fails:

1. The ZK circuit cannot produce a valid proof
2. The transaction is rejected before reaching the network
3. No state changes occur
4. The client receives an error describing the failure

The last row is enforced at end-of-execution by the VM kernel rather than mid-execution: a transaction that mutates no account state (storage, vault, or nonce) and consumes no notes is rejected. See Empty Transaction for the recommended pattern.

Example: ManagedWallet

#![no_std]
#![feature(alloc_error_handler)]

use miden::{component, component_storage, output_note, Asset, NoteIdx, Word};

#[component_storage]
struct ManagedWalletStorage;

#[component]
trait ManagedWallet {
    #[account_procedure]
    fn receive_asset(&mut self, asset: Asset);
    #[account_procedure]
    fn send_asset(&mut self, asset: Asset, note_idx: NoteIdx);
    #[account_procedure]
    fn asset_value(&self, asset_id: Word) -> Word;
}

#[component]
impl ManagedWallet for ManagedWalletStorage {
    /// Receive an asset into the vault.
    fn receive_asset(&mut self, asset: Asset) {
        self.add_asset(asset);
    }

    /// Send an asset to an output note, with balance check.
    fn send_asset(&mut self, asset: Asset, note_idx: NoteIdx) {
        self.remove_asset(asset);
        output_note::add_asset(asset, note_idx);
    }

    /// Read the value word stored under an asset ID.
    fn asset_value(&self, asset_id: Word) -> Word {
        self.get_asset(asset_id)
    }
}

To move assets out of an account, create output notes with output_note::add_asset. For signature verification and nonce management, see Authentication.

Full API docs on docs.rs: miden