//! # FRAME //! //! ```no_compile //! ______ ______ ________ ___ __ __ ______ //! /_____/\ /_____/\ /_______/\ /__//_//_/\ /_____/\ //! \::::_\/_\:::_ \ \ \::: _ \ \\::\| \| \ \\::::_\/_ //! \:\/___/\\:(_) ) )_\::(_) \ \\:. \ \\:\/___/\ //! \:::._\/ \: __ `\ \\:: __ \ \\:.\-/\ \ \\::___\/_ //! \:\ \ \ \ `\ \ \\:.\ \ \ \\. \ \ \ \\:\____/\ //! \_\/ \_\/ \_\/ \__\/\__\/ \__\/ \__\/ \_____\/ //! ``` //! //! > **F**ramework for **R**untime **A**ggregation of **M**odularized **E**ntities: Substrate's //! > State Transition Function (Runtime) Framework. //! //! ## Introduction //! //! As described in [`crate::reference_docs::wasm_meta_protocol`], at a high-level Substrate-based //! blockchains are composed of two parts: //! //! 1. A *runtime* which represents the state transition function (i.e. "Business Logic") of a //! blockchain, and is encoded as a WASM blob. //! 2. A node whose primary purpose is to execute the given runtime. #![doc = simple_mermaid::mermaid!("../../../mermaid/substrate_simple.mmd")] //! //! *FRAME is the Substrate's framework of choice to build a runtime.* //! //! FRAME is composed of two major components, **pallets** and a **runtime**. //! //! ## Pallets //! //! A pallet is a unit of encapsulated logic. It has a clearly defined responsibility and can be //! linked to other pallets. In order to be reusable, pallets shipped with FRAME strive to only care //! about its own responsibilities and make as few assumptions about the general runtime as //! possible. A pallet is analogous to a _module_ in the runtime. //! //! A pallet is defined as a `mod pallet` wrapped by the [`frame::pallet`] macro. Within this macro, //! pallet components/parts can be defined. Most notable of these parts are: //! //! - [Config](frame::pallet_macros::config), allowing a pallet to make itself configurable and //! generic over types, values and such. //! - [Storage](frame::pallet_macros::storage), allowing a pallet to define onchain storage. //! - [Dispatchable function](frame::pallet_macros::call), allowing a pallet to define extrinsics //! that are callable by end users, from the outer world. //! - [Events](frame::pallet_macros::event), allowing a pallet to emit events. //! - [Errors](frame::pallet_macros::error), allowing a pallet to emit well-formed errors. //! //! Some of these pallet components resemble the building blocks of a smart contract. While both //! models are programming state transition functions of blockchains, there are crucial differences //! between the two. See [`crate::reference_docs::runtime_vs_smart_contract`] for more. //! //! Most of these components are defined using macros, the full list of which can be found in //! [`frame::pallet_macros`]. //! //! ### Example //! //! The following examples showcases a minimal pallet. #![doc = docify::embed!("src/polkadot_sdk/frame_runtime.rs", pallet)] //! //! //! A runtime is a collection of pallets that are amalgamated together. Each pallet typically has //! some configurations (exposed as a `trait Config`) that needs to be *specified* in the runtime. //! This is done with [`frame::runtime::prelude::construct_runtime`]. //! //! A (real) runtime that actually wishes to compile to WASM needs to also implement a set of //! runtime-apis. These implementation can be specified using the //! [`frame::runtime::prelude::impl_runtime_apis`] macro. //! //! ### Example //! //! The following example shows a (test) runtime that is composing the pallet demonstrated above, //! next to the [`frame::prelude::frame_system`] pallet, into a runtime. #![doc = docify::embed!("src/polkadot_sdk/frame_runtime.rs", runtime)] //! //! ## More Examples //! //! You can find more FRAME examples that revolve around specific features at [`pallet_examples`]. //! //! ## Alternatives 🌈 //! //! There is nothing in the Substrate's node side code-base that mandates the use of FRAME. While //! FRAME makes it very simple to write Substrate-based runtimes, it is by no means intended to be //! the only one. At the end of the day, any WASM blob that exposes the right set of runtime APIs is //! a valid Runtime form the point of view of a Substrate client (see //! [`crate::reference_docs::wasm_meta_protocol`]). Notable examples are: //! //! * writing a runtime in pure Rust, as done in [this template](https://github.com/JoshOrndorff/frameless-node-template). //! * writing a runtime in AssemblyScript,as explored in [this project](https://github.com/LimeChain/subsembly). #[cfg(test)] mod tests { use frame::prelude::*; /// A FRAME based pallet. This `mod` is the entry point for everything else. All /// `#[pallet::xxx]` macros must be defined in this `mod`. Although, frame also provides an /// experimental feature to break these parts into different `mod`s. See [`pallet_examples`] for /// more. #[docify::export] #[frame::pallet(dev_mode)] pub mod pallet { use super::*; /// The configuration trait of a pallet. Mandatory. Allows a pallet to receive types at a /// later point from the runtime that wishes to contain it. It allows the pallet to be /// parameterized over both types and values. #[pallet::config] pub trait Config: frame_system::Config { /// A type that is not known now, but the runtime that will contain this pallet will /// know it later, therefore we define it here as an associated type. type RuntimeEvent: IsType<::RuntimeEvent> + From>; /// A parameterize-able value that we receive later via the `Get<_>` trait. type ValueParameter: Get; /// Similar to [`Config::ValueParameter`], but using `const`. Both are functionally /// equal, but offer different tradeoffs. const ANOTHER_VALUE_PARAMETER: u32; } /// A mandatory struct in each pallet. All functions callable by external users (aka. /// transactions) must be attached to this type (see [`frame::pallet_macros::call`]). For /// convenience, internal (private) functions can also be attached to this type. #[pallet::pallet] pub struct Pallet(PhantomData); /// The events tha this pallet can emit. #[pallet::event] pub enum Event {} /// A storage item that this pallet contains. This will be part of the state root trie/root /// of the blockchain. #[pallet::storage] pub type Value = StorageValue; /// All *dispatchable* call functions (aka. transactions) are attached to `Pallet` in a /// `impl` block. #[pallet::call] impl Pallet { /// This will be callable by external users, and has two u32s as a parameter. pub fn some_dispatchable( _origin: OriginFor, _param: u32, _other_para: u32, ) -> DispatchResult { Ok(()) } } } /// A simple runtime that contains the above pallet and `frame_system`, the mandatory pallet of /// all runtimes. This runtime is for testing, but it shares a lot of similarities with a *real* /// runtime. #[docify::export] pub mod runtime { use super::pallet as pallet_example; use frame::{prelude::*, testing_prelude::*}; // The major macro that amalgamates pallets into `enum Runtime` construct_runtime!( pub enum Runtime { System: frame_system, Example: pallet_example, } ); // These `impl` blocks specify the parameters of each pallet's `trait Config`. #[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)] impl frame_system::Config for Runtime { type Block = MockBlock; } impl pallet_example::Config for Runtime { type RuntimeEvent = RuntimeEvent; type ValueParameter = ConstU32<42>; const ANOTHER_VALUE_PARAMETER: u32 = 42; } } }