Watch User Fee Token

fee.watchSetUserToken

Watches UserTokenSet events on the fee manager.

Usage

import {  } from './viem.config'
 
const  = ..()
 
.(() => {
  for (const  of ) .(.)
{  user: '0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266',  token: '0x20c0000000000000000000000000000000000001'}
})
 
// Later, tear down the watcher.
.()

import { ,  } from 'viem/tempo'
 
export const  = .({
  : .('0x...'),
})

Also callable standalone: Actions.fee.watchSetUserToken(client, options), with Actions imported from 'viem/tempo'.

Recipes

Invalidate Cached Preferences for Your Users

Filter with args.user to react only when one of your users changes their preference, such as invalidating a fee token cached by a wallet backend.

import {  } from './viem.config'
 
const  = ..({
  : {
    : [
      '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEbb',
      '0x8ba1f109551bD432803012645Ac136ddd64DBA72',
    ],
  },
})
 
.(() => {
  for (const  of )
    .('Preference changed:', .., ..)
})

import { ,  } from 'viem/tempo'
 
export const  = .({
  : .('0x...'),
})

Backfill Changes After Downtime

Pass fromBlock to replay events from the last block your indexer processed before continuing live.

import {  } from './viem.config'
 
const  = ..({
  : 1_234_567n,
})
 
.(() => {
  for (const  of ) .(.., ..)
})

import { ,  } from 'viem/tempo'
 
export const  = .({
  : .('0x...'),
})

Return Value

Returns a watcher handle. Watching starts when the first listener (or async iterator) attaches, and stops when off is called.

type ReturnType = {
  /** Registers a log listener. Starts the watcher on first registration. Returns an unregister function. */
  onLogs: (fn: (logs: readonly Log[]) => void) => () => void
  /** Registers an error listener. Returns an unregister function. */
  onError: (fn: (error: Error) => void) => () => void
  /** Tears down the watcher: removes listeners, ends iterators, stops the poll or subscription. */
  off: () => void
  /** Async-iterates emitted log batches (latest-only stream). */
  [Symbol.asyncIterator]: () => AsyncIterableIterator<{ logs: readonly Log[] }>
}

Each log is decoded, with the event arguments on args:

type Log = {
  /** Decoded `UserTokenSet` event arguments. */
  args: {
    /** Account whose default fee token was set. */
    user: Address
    /** Token set as the account's default fee token. */
    token: Address
  }
  /** Name of the emitted event. */
  eventName: 'UserTokenSet'
  // ...standard log fields (address, blockHash, blockNumber, logIndex, transactionHash, ...)
}

Parameters

args

Type: object

type Args = {
  /** Filter by account address. */
  user?: Address | Address[] | null
}

Indexed argument values to filter logs by.

batch

Type: boolean
Default: true

Whether to batch the logs found within a poll interval into a single emission. When false, each log is emitted on its own.

fromBlock

Type: bigint

Block number from which to start watching for logs.

poll

Type: boolean

Whether to poll for new logs instead of using a subscription. Defaults to true when the transport cannot subscribe or fromBlock is provided.

pollingInterval

Type: number
Default: client.pollingInterval

Polling frequency (in ms).

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