Crate frame_system

System Module

The System module provides low-level access to core types and cross-cutting utilities. It acts as the base layer for other pallets to interact with the Substrate framework components.

• system::Trait

Overview

The System module defines the core data types used in a Substrate runtime. It also provides several utility functions (see Module) for other FRAME pallets.

In addition, it manages the storage items for extrinsics data, indexes, event records, and digest items, among other things that support the execution of the current block.

It also handles low-level tasks like depositing logs, basic set up and take down of temporary storage entries, and access to previous block hashes.

Interface

Dispatchable Functions

The System module does not implement any dispatchable functions.

Public Functions

See the Module struct for details of publicly available functions.

Signed Extensions

The System module defines the following extensions:

• CheckWeight: Checks the weight and length of the block and ensure that it does not exceed the limits.
• CheckNonce: Checks the nonce of the transaction. Contains a single payload of type T::Index.
• CheckEra: Checks the era of the transaction. Contains a single payload of type Era.
• CheckGenesis: Checks the provided genesis hash of the transaction. Must be a part of the signed payload of the transaction.
• CheckSpecVersion: Checks that the runtime version is the same as the one used to sign the transaction.
• CheckTxVersion: Checks that the transaction version is the same as the one used to sign the transaction.

Lookup the runtime aggregator file (e.g. node/runtime) to see the full list of signed extensions included in a chain.

Usage

Prerequisites

Import the System module and derive your module’s configuration trait from the system trait.

Example - Get extrinsic count and parent hash for the current block

use frame_support::{decl_module, dispatch};
use frame_system::{self as system, ensure_signed};

pub trait Trait: system::Trait {}

decl_module! {
	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
		#[weight = 0]
		pub fn system_module_example(origin) -> dispatch::DispatchResult {
			let _sender = ensure_signed(origin)?;
			let _extrinsic_count = <system::Module<T>>::extrinsic_count();
			let _parent_hash = <system::Module<T>>::parent_hash();
			Ok(())
		}
	}
}

Modules

offchain

Module helpers for off-chain calls.

Structs

Account	The full account information for a particular account ID.
AccountInfo	Information of an account.
BlockHash	Map of block numbers to block hashes.
CallKillAccount	Event handler which calls kill_account when it happens.
CallOnCreatedAccount	Event handler which calls on_created_account when it happens.
ChainContext
CheckEra	Check for transaction mortality.
CheckGenesis	Genesis hash check to provide replay protection between different networks.
CheckMortality	Check for transaction mortality.
CheckNonce	Nonce check and increment to give replay protection for transactions.
CheckSpecVersion	Ensure the runtime version registered in the transaction is the same as at present.
CheckTxVersion	Ensure the transaction version registered in the transaction is the same as at present.
CheckWeight	Block resource (weight) limit check.
EnsureNever
EnsureNone
EnsureOneOf	The “OR gate” implementation of EnsureOrigin.
EnsureRoot
EnsureSigned
EnsureSignedBy
EventRecord	Record of an event happening.
GenesisConfig	Genesis config for the module, allow to build genesis storage.
LastRuntimeUpgrade	Stores the spec_version and spec_name of when the last runtime upgrade happened.
LastRuntimeUpgradeInfo	Stores the spec_version and spec_name of when the last runtime upgrade happened.
Module

Enums

Call	Dispatchable calls.
Error	Error for the System module
InitKind	A type of block initialization to perform.
Phase	A phase of a block’s execution.
RawEvent	Events for this module.
RawOrigin	Origin for the System module.
RefStatus	Reference status; can be either referenced or unreferenced.

Traits

Trait
WeightInfo

Functions

ensure_none	Ensure that the origin o represents an unsigned extrinsic. Returns Ok or an Err otherwise.
ensure_root	Ensure that the origin o represents the root. Returns Ok or an Err otherwise.
ensure_signed	Ensure that the origin o represents a signed extrinsic (i.e. transaction). Returns Ok with the account that signed the extrinsic or an Err otherwise.
extrinsics_data_root	Compute the trie root of a list of extrinsics.
extrinsics_root	Compute the trie root of a list of extrinsics.
split_inner	Split an option into two constituent options, as defined by a splitter function.

Type Definitions

DigestItemOf
DigestOf
Event	RawEvent specialized for the configuration Trait
Key
KeyValue
Origin	Exposed trait-generic origin type.
RefCount	Type used to encode the number of references an account has.