pezkuwi_sdk_docs/reference_docs/

frame_tokens.rs

// This file is part of pezkuwi-sdk.
//
// Copyright (C) Parity Technologies (UK) Ltd. and Dijital Kurdistan Tech Institute
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! # FRAME Tokens
//!
//! This reference doc serves as a high-level overview of the token-related logic in FRAME, and
//! how to properly apply it to your use case.
//!
//! On completion of reading this doc, you should have a good understanding of:
//! - The distinction between token traits and trait implementations in FRAME, and why this
//!   distinction is helpful.
//! - Token-related traits available in FRAME.
//! - Token-related trait implementations in FRAME.
//! - How to choose the right trait or trait implementation for your use case.
//! - Where to go next.
//!
//! ## Getting Started
//!
//! The most ubiquitous way to add a token to a FRAME runtime is [`pezpallet_balances`]. Read
//! more about pallets [here](crate::pezkuwi_sdk::frame_runtime#pallets).
//!
//! You may then write custom pallets that interact with [`pezpallet_balances`]. The fastest way to
//! get started with that is by
//! [tightly coupling](crate::reference_docs::frame_pallet_coupling#tight-coupling-pallets) your
//! custom pezpallet to [`pezpallet_balances`].
//!
//! However, to keep pallets flexible and modular, it is often preferred to
//! [loosely couple](crate::reference_docs::frame_pallet_coupling#loosely--coupling-pallets).
//!
//! To achieve loose coupling,
//! we separate token logic into traits and trait implementations.
//!
//! ## Traits and Trait Implementations
//!
//! Broadly speaking, token logic in FRAME can be divided into two categories: traits and
//! trait implementations.
//!
//! **Traits** define common interfaces that types of tokens should implement. For example, the
//! [`fungible::Inspect`](`pezframe_support::traits::fungible::Inspect`) trait specifies an
//! interface for *inspecting* token state such as the total issuance of the token, the balance of
//! individual accounts, etc.
//!
//! **Trait implementations** are concrete implementations of these traits. For example, one of the
//! many traits [`pezpallet_balances`] implements is
//! [`fungible::Inspect`](`pezframe_support::traits::fungible::Inspect`)[^1]. It provides the
//! concrete way of inspecting the total issuance, balance of accounts, etc. There can be many
//! implementations of the same traits.
//!
//! [^1]: Rust Advanced Tip: The knowledge that [`pezpallet_balances`] implements
//! [`fungible::Inspect`](`pezframe_support::traits::fungible::Inspect`) is not some arcane
//! knowledge that you have to know by heart or memorize. One can simply look at the list of the
//! implementors of any trait in the Rust Doc to find all implementors (e.g.
//! [Mutate trait implementors](https://docs.pezkuwichain.io/sdk/master/pezframe_support/traits/tokens/fungible/trait.Mutate.html#implementors)),
//! or use the `rust-analyzer`'s `Implementations` action.
//!
//! The distinction between traits and trait implementations is helpful because it allows pallets
//! and other logic to be generic over their dependencies, avoiding tight coupling.
//!
//! To illustrate this with an example let's consider [`pezpallet_preimage`]. This pezpallet takes a
//! deposit in exchange for storing a preimage for later use. A naive implementation of the
//! pezpallet may use [`pezpallet_balances`] in a tightly coupled manner, directly calling methods
//! on the pezpallet to reserve and unreserve deposits. This approach works well,
//! until someone has a use case requiring that an asset from a different pezpallet such as
//! [`pezpallet_assets`] is used for the deposit. Rather than tightly coupling
//! [`pezpallet_preimage`] to [`pezpallet_balances`], [`pezpallet_assets`], and every other
//! token-handling pezpallet, a user could possibly specify that [`pezpallet_preimage`] does not
//! specify a concrete pezpallet as a dependency, but instead accepts any dependency which
//! implements the
//! [`currency::ReservableCurrency`](`pezframe_support::traits::tokens::currency::ReservableCurrency`)
//! trait, namely via its [`Config::Currency`](`pezpallet_preimage::pezpallet::Config::Currency`)
//! associated type. This allows [`pezpallet_preimage`] to support any arbitrary pezpallet
//! implementing this trait, without needing any knowledge of what those pallets may be or requiring
//! changes to support new pallets which may be written in the future.
//!
//! Read more about coupling, and the benefits of loose coupling
//! [here](crate::reference_docs::frame_pallet_coupling).
//!
//! ## Fungible Token Traits in FRAME
//!
//! The [`fungible`](`pezframe_support::traits::fungible`) crate contains the latest set of FRAME
//! fungible token traits, and is recommended to use for all new logic requiring a fungible token.
//! See the crate documentation for more info about these fungible traits.
//!
//! [`fungibles`](`pezframe_support::traits::fungibles`) provides very similar functionality to
//! [`fungible`](`pezframe_support::traits::fungible`), except it supports managing multiple tokens.
//!
//! You may notice the trait [`Currency`](`pezframe_support::traits::Currency`) with similar
//! functionality is also used in the codebase, however this trait is deprecated and existing logic
//! is in the process of being migrated to [`fungible`](`pezframe_support::traits::fungible`) ([tracking issue](https://github.com/pezkuwichain/pezkuwi-sdk/issues/248)).
//!
//! ## Fungible Token Trait Implementations in FRAME
//!
//! [`pezpallet_balances`] implements [`fungible`](`pezframe_support::traits::fungible`), and is the
//! most commonly used fungible implementation in FRAME. Most of the time, it's used for managing
//! the native token of the blockchain network it's used in.
//!
//! [`pezpallet_assets`] implements [`fungibles`](`pezframe_support::traits::fungibles`), and is
//! another popular fungible token implementation. It supports the creation and management of
//! multiple assets in a single crate, making it a good choice when a network requires more assets
//! in addition to its native token.
//!
//! ## Non-Fungible Tokens in FRAME
//!
//! [`pezpallet_nfts`] is recommended to use for all NFT use cases in FRAME.
//! See the crate documentation for more info about this pezpallet.
//!
//! [`pezpallet_uniques`] is deprecated and should not be used.
//!
//!
//! # What Next?
//!
//! - If you are interested in implementing a single fungible token, continue reading the
//!   [`fungible`](`pezframe_support::traits::fungible`) and [`pezpallet_balances`] docs.
//! - If you are interested in implementing a set of fungible tokens, continue reading the
//!   [`fungibles`](`pezframe_support::traits::fungibles`) trait and [`pezpallet_assets`] docs.
//! - If you are interested in implementing an NFT, continue reading the [`pezpallet_nfts`] docs.