Approve Token Spending

Approves a spender to transfer TIP-20 tokens on behalf of the caller.

Usage

import { client } from './viem.config'
 
const { receipt } = await client.token.approveSync({
  amount: { formatted: '10.5' },
  spender: '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb',
  token: '0x20c0000000000000000000000000000000000000',
})
 
console.log('Transaction hash:', receipt.transactionHash)
Transaction hash: 0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef

import { Account, Client } from 'viem/tempo'
 
export const client = Client.create({
  account: Account.fromSecp256k1('0x...'),
})

Undeclared Tokens

Formatted amounts resolve decimals from the Client's declared tokens (the pathUSD address above is declared on the default token set). For a token not declared on the Client, include amount.decimals so the formatted amount can be parsed.

import { client } from './viem.config'
 
const { receipt } = await client.token.approveSync({
  amount: { decimals: 6, formatted: '10.5' },
  spender: '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb',
  token: '0x20c0000000000000000000000000000000000001',
})

import { Account, Client } from 'viem/tempo'
 
export const client = Client.create({
  account: Account.fromSecp256k1('0x...'),
})

Base Amounts

Pass a bigint to use the token's base unit amount directly.

import { client } from './viem.config'
 
const { receipt } = await client.token.approveSync({
  amount: 10500000n,
  spender: '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb',
  token: '0x20c0000000000000000000000000000000000000',
})

import { Account, Client } from 'viem/tempo'
 
export const client = Client.create({
  account: Account.fromSecp256k1('0x...'),
})

Asynchronous Usage

The examples above use a *Sync variant of the action, that will wait for the transaction to be included before returning.

If you are optimizing for performance, you should use the non-sync token.approve action and wait for inclusion manually:

import { Actions } from 'viem/tempo'
import { client } from './viem.config'
 
const hash = await client.token.approve({
  amount: { formatted: '10.5' },
  spender: '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb',
  token: '0x20c0000000000000000000000000000000000000',
})
const receipt = await client.transaction.waitForReceipt({ hash }).receipt
 
const { args } = Actions.token.approve.extractEvent(receipt.logs)

Recipes

Fund Subscription Billing with an Allowance

Use an allowance to let your billing service charge on schedule: the customer approves a period's budget once, then the server pulls each charge with token.transferSync.

import { client } from './viem.config'
 
const { receipt } = await client.token.approveSync({
  amount: { formatted: '120' },
  spender: '0x8ba1f109551bD432803012645Ac136ddd64DBA72',
  token: '0x20c0000000000000000000000000000000000000',
})

import { client } from './viem.config'
 
const { receipt } = await client.token.transferSync({
  amount: { formatted: '10' },
  from: '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb',
  to: '0x8ba1f109551bD432803012645Ac136ddd64DBA72',
  token: '0x20c0000000000000000000000000000000000000',
})

import { Account, Client } from 'viem/tempo'
 
export const client = Client.create({
  account: Account.fromSecp256k1('0x...'),
})

Revoke a Compromised Spender

Set amount to 0n to cut off a spender immediately, then confirm with token.getAllowance, for example after a billing integration is compromised.

import { client } from './viem.config'
 
const spender = '0x8ba1f109551bD432803012645Ac136ddd64DBA72'
const token = '0x20c0000000000000000000000000000000000000'
 
const { receipt } = await client.token.approveSync({
  amount: 0n,
  spender,
  token,
})
 
const allowance = await client.token.getAllowance({
  account: client.account.address,
  spender,
  token,
})
 
console.log('Remaining allowance:', allowance.formatted)
Remaining allowance: 0

import { Account, Client } from 'viem/tempo'
 
export const client = Client.create({
  account: Account.fromSecp256k1('0x...'),
})

Return Value

type ReturnType = {
  /** Owner that approved the spender. */
  owner: Address
  /** Spender approved to transfer the tokens. */
  spender: Address
  /** Approved amount, in base units. */
  amount: bigint
  /** Token decimals used to derive `formatted`, if known. */
  decimals?: number | undefined
  /** Approved amount formatted with the token's `decimals`, if known. */
  formatted?: string | undefined
  /** Transaction receipt. */
  receipt: TransactionReceipt
}

Parameters

amount

• Type: bigint | { decimals?: number, formatted: string }

Amount to approve, in base units or formatted decimal form. Include amount.decimals when the token is not declared on the Client's tokens.

spender

• Type: Address

Address of the spender.

token

• Type: Address | bigint

Token to operate on: a TIP-20 token id or a contract address.

account (optional)

• Type: Account | Address

Account that will be used to send the transaction.

feePayer (optional)

• Type: Account | boolean

Fee payer for the transaction (TIP-1 gas sponsorship).

Pass true to defer the fee token to an external fee payer (e.g. a relay), or a local Account to co-sign the transaction as the fee payer.

feeToken (optional)

• Type: Address | bigint

Fee token for the transaction.

Can be an unpaused USD-denominated TIP-20 token address or ID.

gas (optional)

• Type: bigint

Gas limit for the transaction.

keyAuthorization (optional)

• Type: KeyAuthorization

Signed key authorization to include with the transaction, authorizing an access key to act for the sending account.

maxFeePerGas (optional)

• Type: bigint

Max fee per gas for the transaction.

maxPriorityFeePerGas (optional)

• Type: bigint

Max priority fee per gas for the transaction.

nonce (optional)

• Type: number

Nonce for the transaction.

nonceKey (optional)

• Type: 'expiring' | 'random' | bigint

Nonce key for the transaction (TIP-1009 2D nonces).

Use 'expiring' to select an expiring nonce, which enables concurrent transaction submission without nonce ordering. Use 'random' to select a random key.

throwOnReceiptRevert (optional)

• Type: boolean
• Default: true

Whether a Sync action throws when the receipt reports a revert.

validAfter (optional)

• Type: number

Unix timestamp after which the transaction can be included.

validBefore (optional)

• Type: number

Unix timestamp before which the transaction must be included.