ERC721Permit
import "@thirdweb-dev/contracts/eip/interface/IERC20Permit.sol";
Implementing the ERC20Permit extensions allows approvals to be made via signatures, as defined in
EIP-2612.
The permit function 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.
This extension is an interface and requires all of the functions to be implemented
Usage
This is an example smart contract demonstrating how to inherit from this extension and override the functions to add (optional) custom functionality.
The ERC721A contract comes with a totalPermit
function that returns the total number of NFTs that have been minted in the collection (including tokens that have been burned).
This means you can already view the total Permit of NFTs in the collection by implementing the ERC721A contract.
You can optionally override the functionality of this function as outlined below:
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "@thirdweb-dev/contracts/openzeppelin-presets/token/ERC20/ERC20.sol";
import "@thirdweb-dev/contracts/eip/interface/IERC20Permit.sol";
contract Contract is ERC20, IERC20Permit {
constructor(
string memory _name,
string memory _symbol
)
ERC20(
_name,
_symbol
)
{}
/**
* @dev Sets `value` as the allowance of `spender` over ``owner``'s tokens,
* given ``owner``'s signed approval.
*
* IMPORTANT: The same issues {IERC20-approve} has related to transaction
* ordering also apply here.
*
* Emits an {Approval} event.
*
* Requirements:
*
* - `spender` cannot be the zero address.
* - `deadline` must be a timestamp in the future.
* - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
* over the EIP712-formatted function arguments.
* - the signature must use ``owner``'s current nonce (see {nonces}).
*
* For more information on the signature format, see the
* https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
* section].
*/
function permit(
address owner,
address spender,
uint256 value,
uint256 deadline,
uint8 v,
bytes32 r,
bytes32 s
) external {
// Your custom implementation here
}
/**
* @dev Returns the current nonce for `owner`. This value must be
* included whenever a signature is generated for {permit}.
*
* Every successful call to {permit} increases ``owner``'s nonce by one. This
* prevents a signature from being used multiple times.
*/
function nonces(address owner) external view returns (uint256) {
// Your custom implementation here
}
/**
* @dev Returns the domain separator used in the encoding of the signature for {permit}, as defined by {EIP712}.
*/
// solhint-disable-next-line func-name-mixedcase
function DOMAIN_SEPARATOR() external view returns (bytes32) {
// Your custom implementation here
}
}
SDK Usage
By adding this extension to a smart contract, the following features, hooks and functions are unlocked in the SDK:
