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IERC20Permit

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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;

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);

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);