IAllowance

Asset Tokenization Studio Team

IAllowance

Consolidated interface for the ERC-20 allowance domain: granting, reading and atomically adjusting spender allowances.

Methods

allowance

function allowance(address _owner, address _spender) external view returns (uint256)

Returns the remaining amount spender may spend on behalf of owner via a downstream transferFrom-style call.

Zero by default. Updated by {approve}, {increaseAllowance}, {decreaseAllowance} and by any consuming transfer operation. The returned value is time-travel adjusted at the current block timestamp on the implementing facet.

Parameters

Name	Type	Description
_owner	address	Address that granted the allowance.
_spender	address	Address authorised to spend on owner's behalf.

Returns

Name	Type	Description
_0	uint256	Remaining allowance of spender over owner's tokens.

approve

function approve(address _spender, uint256 _value) external nonpayable returns (bool)

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

Overwrites any previously-granted allowance. Known race: moving a non-zero allowance directly to another non-zero value lets spender spend both the old and the new amount via unfortunate transaction ordering — see EIP-20 discussion https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729. Prefer {increaseAllowance}/{decreaseAllowance}, or reset to zero before setting a new value. Emits {IAllowanceTypes.Approval} with the resulting allowance.

Parameters

Name	Type	Description
_spender	address	Address authorised to spend on the caller's behalf.
_value	uint256	Absolute allowance amount to grant.

Returns

Name	Type	Description
_0	bool	Boolean flag indicating whether the operation succeeded.

decreaseAllowance

function decreaseAllowance(address _spender, uint256 _subtractedValue) external nonpayable returns (bool)

Atomically decreases the allowance granted to spender by the caller.

Preferred alternative to {approve} as it avoids the read-modify-write allowance race. Reverts with {IAllowanceTypes.SpenderWithZeroAddress} when spender is the zero address, or with {IAllowanceTypes.InsufficientAllowance} when the current allowance is below subtractedValue. Emits {IAllowanceTypes.Approval} with the resulting allowance.

Parameters

Name	Type	Description
_spender	address	Address whose allowance is being decreased.
_subtractedValue	uint256	Amount subtracted from the existing allowance.

Returns

Name	Type	Description
_0	bool	Boolean flag indicating whether the operation succeeded.

increaseAllowance

function increaseAllowance(address _spender, uint256 _addedValue) external nonpayable returns (bool)

Atomically increases the allowance granted to spender by the caller.

Preferred alternative to {approve} as it avoids the read-modify-write allowance race. Reverts with {IAllowanceTypes.SpenderWithZeroAddress} when spender is the zero address. Emits {IAllowanceTypes.Approval} with the resulting allowance.

Parameters

Name	Type	Description
_spender	address	Address whose allowance is being increased.
_addedValue	uint256	Amount added to the existing allowance.

Returns

Name	Type	Description
_0	bool	Boolean flag indicating whether the operation succeeded.

initializeAllowance

function initializeAllowance() external nonpayable

Initialises the allowance capability on the token.

Callable once; subsequent calls revert with FacetAlreadyRegistered. Requires DEFAULT_ADMIN_ROLE. Called by the factory during deployment.

Events

AllowanceInitialized

event AllowanceInitialized()

Emitted once when the allowance capability is initialised on a token.

Fires exclusively from initializeAllowance after the storage write succeeds.

Approval

event Approval(address indexed owner, address indexed spender, uint256 value)

Emitted when owner authorises spender to spend up to value tokens on their behalf, whether via {IAllowance.approve}, {IAllowance.increaseAllowance} or {IAllowance.decreaseAllowance}.

Mirrors the ERC-20 Approval event. value is the resulting, absolute allowance after the update — not the delta applied.

Parameters

Name	Type	Description
owner indexed	address	Address whose tokens may be spent.
spender indexed	address	Address authorised to spend on owner's behalf.
value	uint256	Allowance of spender over owner's tokens after the update.

Errors

InfiniteAllowance

error InfiniteAllowance(address owner, address spender)

Raised when an operation encounters an allowance that is effectively unlimited.

Indicates that the owner has granted the spender an infinite allowance, which may require special handling to avoid unintended accounting or revocation assumptions.

Parameters

Name	Type	Description
owner	address	The account that granted the allowance.
spender	address	The account authorised to spend on behalf of the owner.

InsufficientAllowance

error InsufficientAllowance(address spender, address from)

Reverts when spender attempts to consume more allowance than from has granted.

Raised by transferFrom-style flows and by {IAllowance.decreaseAllowance} when the subtracted amount exceeds the current allowance.

Parameters

Name	Type	Description
spender	address	Address attempting to spend on behalf of from.
from	address	Address whose allowance is being consumed.

SpenderWithZeroAddress

error SpenderWithZeroAddress()

Reverts when the zero address is supplied as spender in an allowance update.