IERC20Permit

Git Source

Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].

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.

Functions

permit

Sets value as th xe 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;

Parameters

Name	Type	Description
owner	address
spender	address
value	uint256
deadline	uint256
v	uint8
r	bytes32
s	bytes32

nonces

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);

Parameters

Name	Type	Description
owner	address

Returns

Name	Type	Description
<none>	uint256

DOMAIN_SEPARATOR

Returns the domain separator used in the encoding of the signature for permit, as defined by EIP712.

function DOMAIN_SEPARATOR() external view returns (bytes32);

Returns

Name	Type	Description
<none>	bytes32