Bastian Köcher
5d73e960da
The timestamp inherent type was up to now just a simple `u64`. This worked, but doesn't give you that much guarantees at compile time about the type. This pr changes that by converting this type to a unit type wrapper, similar to what we have done for `Slot`. This is required for some future pr that touches quite a lot of the inherents stuff :) Besides this unit wrapper type, this pr also moves the `OnTimestampSet` trait to `frame_support::traits`.
Timestamp Module
The Timestamp module provides functionality to get and set the on-chain time.
Overview
The Timestamp module allows the validators to set and validate a timestamp with each block.
It uses inherents for timestamp data, which is provided by the block author and validated/verified by other validators. The timestamp can be set only once per block and must be set each block. There could be a constraint on how much time must pass before setting the new timestamp.
NOTE: The Timestamp module is the recommended way to query the on-chain time instead of using an approach based on block numbers. The block number based time measurement can cause issues because of cumulative calculation errors and hence should be avoided.
Interface
Dispatchable Functions
set- Sets the current time.
Public functions
get- Gets the current time for the current block. If this function is called prior to setting the timestamp, it will return the timestamp of the previous block.
Config Getters
MinimumPeriod- Gets the minimum (and advised) period between blocks for the chain.
Usage
The following example shows how to use the Timestamp module in your custom module to query the current timestamp.
Prerequisites
Import the Timestamp module into your custom module and derive the module configuration trait from the timestamp trait.
Get current timestamp
use frame_support::{decl_module, dispatch};
use frame_system::ensure_signed;
pub trait Config: timestamp::Config {}
decl_module! {
pub struct Module<T: Config> for enum Call where origin: T::Origin {
#[weight = 0]
pub fn get_time(origin) -> dispatch::DispatchResult {
let _sender = ensure_signed(origin)?;
let _now = <timestamp::Module<T>>::get();
Ok(())
}
}
}
Example from the FRAME
The Session module uses the Timestamp module for session management.
Related Modules
License: Apache-2.0