diff --git a/srml/assets/src/lib.rs b/srml/assets/src/lib.rs index 9caa3dc20d542..3f7c1b3efc153 100644 --- a/srml/assets/src/lib.rs +++ b/srml/assets/src/lib.rs @@ -14,7 +14,108 @@ // You should have received a copy of the GNU General Public License // along with Substrate. If not, see . +//! # 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 [`Trait`](./trait.Trait.html). +//! +//! The supported dispatchable functions are documented in the [`Call`](./enum.Call.html) 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 an `amount` of units of fungible asset `id` from the balance of +//! the function caller's account (`origin`) to a `target` account. +//! * `destroy` - Destroys the entire holding of a fungible asset `id` associated with the account +//! that called the function. +//! +//! Please refer to the [`Call`](./enum.Call.html) enum and its associated variants for documentation on each function. +//! +//! ### Public Functions +//! +//! +//! * `balance` - Get the asset `id` balance of `who`. +//! * `total_supply` - Get the total supply of an asset `id`. +//! +//! Please refer to the [`Module`](./struct.Module.html) 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 +//! +//! ```rust,ignore +//! use support::{decl_module, dispatch::Result}; +//! use system::ensure_signed; +//! +//! pub trait Trait: assets::Trait { } +//! +//! decl_module! { +//! pub struct Module for enum Call where origin: T::Origin { +//! pub fn issue_token_airdrop(origin) -> Result { +//! const ACCOUNT_ALICE: u64 = 1; +//! const ACCOUNT_BOB: u64 = 2; +//! const COUNT_AIRDROP_RECIPIENTS = 2; +//! const TOKENS_FIXED_SUPPLY: u64 = 100; +//! +//! ensure!(!COUNT_AIRDROP_RECIPIENTS.is_zero(), "Divide by zero error."); +//! +//! let sender = ensure_signed(origin)?; +//! let asset_id = Self::next_asset_id(); +//! +//! >::mutate(|asset_id| *asset_id += 1); +//! >::insert((asset_id, &ACCOUNT_ALICE), TOKENS_FIXED_SUPPLY / COUNT_AIRDROP_RECIPIENTS); +//! >::insert((asset_id, &ACCOUNT_BOB), TOKENS_FIXED_SUPPLY / COUNT_AIRDROP_RECIPIENTS); +//! >::insert(asset_id, TOKENS_FIXED_SUPPLY); +//! +//! Self::deposit_event(RawEvent::Issued(asset_id, sender, TOKENS_FIXED_SUPPLY)); +//! Ok(()) +//! } +//! } +//! } +//! ``` +//! +//! ## Related Modules +//! +//! * [`System`](../srml_system/index.html) +//! * [`Support`](../srml_support/index.html) // Ensure we're `no_std` when compiling for Wasm. #![cfg_attr(not(feature = "std"), no_std)] @@ -23,6 +124,7 @@ use srml_support::{StorageValue, StorageMap, Parameter, decl_module, decl_event, use primitives::traits::{Member, SimpleArithmetic, Zero, StaticLookup}; use system::ensure_signed; +/// The module configuration trait. pub trait Trait: system::Trait { /// The overarching event type. type Event: From> + Into<::Event>; @@ -34,7 +136,6 @@ pub trait Trait: system::Trait { type AssetId = u32; decl_module! { - // Simple declaration of the `Module` type. Lets the macro know what its working on. pub struct Module for enum Call where origin: T::Origin { fn deposit_event() = default; /// Issue a new class of fungible assets. There are, and will only ever be, `total` @@ -99,7 +200,7 @@ decl_storage! { Balances: map (AssetId, T::AccountId) => T::Balance; /// The next asset identifier up for grabs. NextAssetId get(next_asset_id): AssetId; - /// The total unit supply of an asset + /// The total unit supply of an asset. TotalSupply: map AssetId => T::Balance; } } @@ -113,7 +214,7 @@ impl Module { >::get((id, who)) } - // Get the total supply of an asset `id` + /// Get the total supply of an asset `id`. pub fn total_supply(id: AssetId) -> T::Balance { >::get(id) }