# frame_tokens.rs - source
Source of the Rust file `docs/sdk/src/reference_docs/frame_tokens.rs`.

#
pezkuwi_sdk_docs/reference_docs/
frame_tokens.rs

    1// This file is part of pezkuwi-sdk.
    2//
    3// Copyright (C) Parity Technologies (UK) Ltd. and Dijital Kurdistan Tech Institute
    4// SPDX-License-Identifier: Apache-2.0
    5//
    6// Licensed under the Apache License, Version 2.0 (the "License");
    7// you may not use this file except in compliance with the License.
    8// You may obtain a copy of the License at
    9//
    10// 	http://www.apache.org/licenses/LICENSE-2.0
    11//
    12// Unless required by applicable law or agreed to in writing, software
    13// distributed under the License is distributed on an "AS IS" BASIS,
    14// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    15// See the License for the specific language governing permissions and
    16// limitations under the License.
    17
    18//! # FRAME Tokens
    19//!
    20//! This reference doc serves as a high-level overview of the token-related logic in FRAME, and
    21//! how to properly apply it to your use case.
    22//!
    23//! On completion of reading this doc, you should have a good understanding of:
    24//! - The distinction between token traits and trait implementations in FRAME, and why this
    25//!   distinction is helpful.
    26//! - Token-related traits available in FRAME.
    27//! - Token-related trait implementations in FRAME.
    28//! - How to choose the right trait or trait implementation for your use case.
    29//! - Where to go next.
    30//!
    31//! ## Getting Started
    32//!
    33//! The most ubiquitous way to add a token to a FRAME runtime is [`pezpallet_balances`]. Read
    34//! more about pallets [here](crate::pezkuwi_sdk::frame_runtime#pallets).
    35//!
    36//! You may then write custom pallets that interact with [`pezpallet_balances`]. The fastest way to
    37//! get started with that is by
    38//! [tightly coupling](crate::reference_docs::frame_pallet_coupling#tight-coupling-pallets) your
    39//! custom pezpallet to [`pezpallet_balances`].
    40//!
    41//! However, to keep pallets flexible and modular, it is often preferred to
    42//! [loosely couple](crate::reference_docs::frame_pallet_coupling#loosely--coupling-pallets).
    43//!
    44//! To achieve loose coupling,
    45//! we separate token logic into traits and trait implementations.
    46//!
    47//! ## Traits and Trait Implementations
    48//!
    49//! Broadly speaking, token logic in FRAME can be divided into two categories: traits and
    50//! trait implementations.
    51//!
    52//! **Traits** define common interfaces that types of tokens should implement. For example, the
    53//! [`fungible::Inspect`](`pezframe_support::traits::fungible::Inspect`) trait specifies an
    54//! interface for *inspecting* token state such as the total issuance of the token, the balance of
    55//! individual accounts, etc.
    56//!
    57//! **Trait implementations** are concrete implementations of these traits. For example, one of the
    58//! many traits [`pezpallet_balances`] implements is
    59//! [`fungible::Inspect`](`pezframe_support::traits::fungible::Inspect`)[^1]. It provides the
    60//! concrete way of inspecting the total issuance, balance of accounts, etc. There can be many
    61//! implementations of the same traits.
    62//!
    63//! [^1]: Rust Advanced Tip: The knowledge that [`pezpallet_balances`] implements
    64//! [`fungible::Inspect`](`pezframe_support::traits::fungible::Inspect`) is not some arcane
    65//! knowledge that you have to know by heart or memorize. One can simply look at the list of the
    66//! implementors of any trait in the Rust Doc to find all implementors (e.g.
    67//! [Mutate trait implementors](https://docs.pezkuwichain.io/sdk/master/pezframe_support/traits/tokens/fungible/trait.Mutate.html#implementors)),
    68//! or use the `rust-analyzer`'s `Implementations` action.
    69//!
    70//! The distinction between traits and trait implementations is helpful because it allows pallets
    71//! and other logic to be generic over their dependencies, avoiding tight coupling.
    72//!
    73//! To illustrate this with an example let's consider [`pezpallet_preimage`]. This pezpallet takes a
    74//! deposit in exchange for storing a preimage for later use. A naive implementation of the
    75//! pezpallet may use [`pezpallet_balances`] in a tightly coupled manner, directly calling methods
    76//! on the pezpallet to reserve and unreserve deposits. This approach works well,
    77//! until someone has a use case requiring that an asset from a different pezpallet such as
    78//! [`pezpallet_assets`] is used for the deposit. Rather than tightly coupling
    79//! [`pezpallet_preimage`] to [`pezpallet_balances`], [`pezpallet_assets`], and every other
    80//! token-handling pezpallet, a user could possibly specify that [`pezpallet_preimage`] does not
    81//! specify a concrete pezpallet as a dependency, but instead accepts any dependency which
    82//! implements the
    83//! [`currency::ReservableCurrency`](`pezframe_support::traits::tokens::currency::ReservableCurrency`)
    84//! trait, namely via its [`Config::Currency`](`pezpallet_preimage::pezpallet::Config::Currency`)
    85//! associated type. This allows [`pezpallet_preimage`] to support any arbitrary pezpallet
    86//! implementing this trait, without needing any knowledge of what those pallets may be or requiring
    87//! changes to support new pallets which may be written in the future.
    88//!
    89//! Read more about coupling, and the benefits of loose coupling
    90//! [here](crate::reference_docs::frame_pallet_coupling).
    91//!
    92//! ## Fungible Token Traits in FRAME
    93//!
    94//! The [`fungible`](`pezframe_support::traits::fungible`) crate contains the latest set of FRAME
    95//! fungible token traits, and is recommended to use for all new logic requiring a fungible token.
    96//! See the crate documentation for more info about these fungible traits.
    97//!
    98//! [`fungibles`](`pezframe_support::traits::fungibles`) provides very similar functionality to
    99//! [`fungible`](`pezframe_support::traits::fungible`), except it supports managing multiple tokens.
    100//!
    101//! You may notice the trait [`Currency`](`pezframe_support::traits::Currency`) with similar
    102//! functionality is also used in the codebase, however this trait is deprecated and existing logic
    103//! is in the process of being migrated to [`fungible`](`pezframe_support::traits::fungible`) ([tracking issue](https://github.com/pezkuwichain/pezkuwi-sdk/issues/248)).
    104//!
    105//! ## Fungible Token Trait Implementations in FRAME
    106//!
    107//! [`pezpallet_balances`] implements [`fungible`](`pezframe_support::traits::fungible`), and is the
    108//! most commonly used fungible implementation in FRAME. Most of the time, it's used for managing
    109//! the native token of the blockchain network it's used in.
    110//!
    111//! [`pezpallet_assets`] implements [`fungibles`](`pezframe_support::traits::fungibles`), and is
    112//! another popular fungible token implementation. It supports the creation and management of
    113//! multiple assets in a single crate, making it a good choice when a network requires more assets
    114//! in addition to its native token.
    115//!
    116//! ## Non-Fungible Tokens in FRAME
    117//!
    118//! [`pezpallet_nfts`] is recommended to use for all NFT use cases in FRAME.
    119//! See the crate documentation for more info about this pezpallet.
    120//!
    121//! [`pezpallet_uniques`] is deprecated and should not be used.
    122//!
    123//!
    124//! # What Next?
    125//!
    126//! - If you are interested in implementing a single fungible token, continue reading the
    127//!   [`fungible`](`pezframe_support::traits::fungible`) and [`pezpallet_balances`] docs.
    128//! - If you are interested in implementing a set of fungible tokens, continue reading the
    129//!   [`fungibles`](`pezframe_support::traits::fungibles`) trait and [`pezpallet_assets`] docs.
    130//! - If you are interested in implementing an NFT, continue reading the [`pezpallet_nfts`] docs.