ERC20Upgradeable

Git Source ↗

Inherits: Initializable ↗, IERC20Permit ↗, IERC20 ↗, IERC20Metadata ↗

Modern and gas efficient ERC20 ↗ + EIP-2612 ↗ implementation.

State Variables

name

Returns the name of the token.

string public override name

symbol

Returns the symbol of the token.

string public override symbol

decimals

Returns the decimals places of the token.

uint8 public constant override decimals = 18

allowance

Returns the remaining number of tokens that spender is allowed to spend on behalf of owner

mapping(address => mapping(address => uint256)) public override allowance

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.

mapping(address => uint256) public override nonces

Functions

approve

Sets amount as the allowance of spender over the caller's tokens.

Front-Running Risk

Be aware of potential front-running attacks. See EIP-20 Discussion ↗ for details.

function approve(address spender, uint256 amount) public override returns (bool);

transfer

Moves amount tokens from the caller's account to to.

function transfer(address to, uint256 amount) public virtual override returns (bool);

transferFrom

Moves amount tokens from from to to using the allowance mechanism. amount is then deducted from the caller's allowance.

function transferFrom(address from, address to, uint256 amount) public virtual override returns (bool);

permit

Sets value as the allowance of spender over owner's tokens using a signed approval.

Security Considerations

• The same front-running issues that affect IERC20-approve also apply here
• Always verify signatures are using the latest nonce
• Be cautious of signature replay attacks

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, see EIP-2612 Specification ↗.

function permit(address owner, address spender, uint256 value, uint256 deadline, uint8 v, bytes32 r, bytes32 s)
    public
    override;

DOMAIN_SEPARATOR

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

function DOMAIN_SEPARATOR() public view override returns (bytes32);