ERC-20 Permit
Adds the permit method, which can be used to change an account’s ERC20 allowance (see IErc20::allowance) by presenting a message signed by the account. By not relying on IErc20::approve, the token holder account doesn’t need to send a transaction, and thus is not required to hold Ether at all.
Usage
In order to have ERC-20 Permit token, you need to use only this contract without ERC-20 as follows:
use openzeppelin_stylus::
token::erc20::{
extensions::{permit, Erc20Permit, IErc20Permit,
Erc20, IErc20,
},
utils::
cryptography::eip712::IEip712,
nonces::{INonces, Nonces,
},
};
#[entrypoint]
#[storage]
struct Erc20PermitExample
erc20: Erc20,
nonces: Nonces,
erc20_permit: Erc20Permit<Eip712>,
#[storage]
struct Eip712;
impl IEip712 for Eip712
const NAME: &'static str = "ERC-20 Permit Example";
const VERSION: &'static str = "1";
#[public]
#[implements(IErc20<Error = permit::Error>, INonces, IErc20Permit<Error = permit::Error>)]
impl Erc20PermitExample
// Add token minting feature.
fn mint(
&mut self,
account: Address,
value: U256,
) -> Result<(), permit::Error> {
Ok(self.erc20._mint(account, value)?)
}
#[public]
impl INonces for Erc20PermitExample
fn nonces(&self, owner: Address) -> U256 {
self.nonces.nonces(owner)
}
#[public]
impl IErc20Permit for Erc20PermitExample
type Error = permit::Error;
#[selector(name = "DOMAIN_SEPARATOR")]
fn domain_separator(&self) -> B256 {
self.erc20_permit.domain_separator()
fn permit(
&mut self,
owner: Address,
spender: Address,
value: U256,
deadline: U256,
v: u8,
r: B256,
s: B256,
) -> Result<(), Self::Error>
self.erc20_permit.permit(
owner,
spender,
value,
deadline,
v,
r,
s,
&mut self.erc20,
&mut self.nonces,
)
}
#[public]
impl IErc20 for Erc20PermitExample
type Error = permit::Error;
fn total_supply(&self) -> U256 {
self.erc20.total_supply()
fn balance_of(&self, account: Address) -> U256
self.erc20.balance_of(account)
fn transfer(
&mut self,
to: Address,
value: U256,
) -> Result<bool, Self::Error>
Ok(self.erc20.transfer(to, value)?)
fn allowance(&self, owner: Address, spender: Address) -> U256
self.erc20.allowance(owner, spender)
fn approve(
&mut self,
spender: Address,
value: U256,
) -> Result<bool, Self::Error>
Ok(self.erc20.approve(spender, value)?)
fn transfer_from(
&mut self,
from: Address,
to: Address,
value: U256,
) -> Result<bool, Self::Error>
Ok(self.erc20.transfer_from(from, to, value)?)
}