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SLoC
Assets Module
A simple, secure module for dealing with fungible assets.
Overview
The Assets module provides functionality for asset management of fungible asset classes with a fixed supply, including:
- Asset Issuance
- Asset Transfer
- Asset Destruction
To use it in your runtime, you need to implement the assets
assets::Config
.
The supported dispatchable functions are documented in the
assets::Call
enum.
Terminology
- Asset issuance: The creation of a new asset, whose total supply will belong to the account that issues the asset.
- Asset transfer: The action of transferring assets from one account to another.
- Asset destruction: The process of an account removing its entire holding of an asset.
- Fungible asset: An asset whose units are interchangeable.
- Non-fungible asset: An asset for which each unit has unique characteristics.
Goals
The assets system in Substrate is designed to make the following possible:
- Issue a unique asset to its creator's account.
- Move assets between accounts.
- Remove an account's balance of an asset when requested by that account's owner and update the asset's total supply.
Interface
Dispatchable Functions
issue
- Issues the total supply of a new fungible asset to the account of the caller of the function.transfer
- Transfers anamount
of units of fungible assetid
from the balance of the function caller's account (origin
) to atarget
account.destroy
- Destroys the entire holding of a fungible assetid
associated with the account that called the function.
Please refer to the Call
enum and its associated
variants for documentation on each function.
Public Functions
balance
- Get the assetid
balance ofwho
.total_supply
- Get the total supply of an assetid
.
Please refer to the Pallet
struct for
details on publicly available functions.
Usage
The following example shows how to use the Assets module in your runtime by exposing public functions to:
- Issue a new fungible asset for a token distribution event (airdrop).
- Query the fungible asset holding balance of an account.
- Query the total supply of a fungible asset that has been issued.
Prerequisites
Import the Assets module and types and derive your runtime's configuration traits from the Assets module trait.
Simple Code Snippet
use pallet_assets as assets;
use sp_runtime::ArithmeticError;
#[frame_support::pallet]
pub mod pallet {
use super::*;
use frame_support::pallet_prelude::*;
use frame_system::pallet_prelude::*;
#[pallet::pallet]
pub struct Pallet<T>(_);
#[pallet::config]
pub trait Config: frame_system::Config + assets::Config {}
#[pallet::call]
impl<T: Config> Pallet<T> {
pub fn issue_token_airdrop(origin: OriginFor<T>) -> DispatchResult {
let sender = ensure_signed(origin)?;
const ACCOUNT_ALICE: u64 = 1;
const ACCOUNT_BOB: u64 = 2;
const COUNT_AIRDROP_RECIPIENTS: u64 = 2;
const TOKENS_FIXED_SUPPLY: u64 = 100;
ensure!(!COUNT_AIRDROP_RECIPIENTS.is_zero(), ArithmeticError::DivisionByZero);
let asset_id = Self::next_asset_id();
<NextAssetId<T>>::mutate(|asset_id| *asset_id += 1);
<Balances<T>>::insert((asset_id, &ACCOUNT_ALICE), TOKENS_FIXED_SUPPLY / COUNT_AIRDROP_RECIPIENTS);
<Balances<T>>::insert((asset_id, &ACCOUNT_BOB), TOKENS_FIXED_SUPPLY / COUNT_AIRDROP_RECIPIENTS);
<TotalSupply<T>>::insert(asset_id, TOKENS_FIXED_SUPPLY);
Self::deposit_event(Event::Issued(asset_id, sender, TOKENS_FIXED_SUPPLY));
Ok(())
}
}
}
Assumptions
Below are assumptions that must be held when using this module. If any of them are violated, the behavior of this module is undefined.
- The total count of assets should be less than
Config::AssetId::max_value()
.
Related Modules
License: Apache-2.0
Release
Polkadot SDK stable2409
Dependencies
~17–32MB
~526K SLoC