Viem Adapter

Integration between the CoW Protocol SDK and the Viem library

Viem Adapter

The Viem Adapter provides integration with the viem library, enabling you to use all CoW Protocol SDK packages with viem clients and accounts.

Installation

npm install @cowprotocol/sdk-viem-adapter

Constructor

import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { http, createPublicClient, privateKeyToAccount } from 'viem'
import { sepolia } from 'viem/chains'

const account = privateKeyToAccount('YOUR_PRIVATE_KEY' as `0x${string}`)
const transport = http('YOUR_RPC_URL')
const provider = createPublicClient({ chain: sepolia, transport })

const adapter = new ViemAdapter({ provider, signer: account })

Parameters

provider · PublicClient · required

A viem createPublicClient instance

signer · Account | `0x${string}`

A viem account from privateKeyToAccount or similar

walletClient · WalletClient

A viem WalletClient, useful with wagmi’s useWalletClient hook

Properties

signer

Returns the ViemSignerAdapter instance. Throws an error if no signer was provided.

const signerAdapter = adapter.signer

utils

Utility methods for working with viem types and contracts.

const iface = adapter.utils.createInterface(abi)

TypedDataVersionedSigner

Signer class for EIP-712 typed data with version support.

TypedDataV3Signer

Signer class for EIP-712 typed data version 3 (legacy).

IntChainIdTypedDataV4Signer

Signer class for EIP-712 typed data version 4 with integer chain ID handling.

Methods

getChainId

Returns the chain ID from the connected provider.

const chainId = await adapter.getChainId()

Returns: Promise<number>

getCode

Returns the bytecode at a given address.

const code = await adapter.getCode('0x...')

• address (string) - Contract address

Returns: Promise<string | undefined>

getTransactionReceipt

Returns the transaction receipt for a given transaction hash.

const receipt = await adapter.getTransactionReceipt('0x...')

• hash (string) - Transaction hash

Returns: Promise<TransactionReceipt | null>

getStorageAt

Returns the value from a storage position at a given address.

const value = await adapter.getStorageAt('0x...', '0x0')

• address (string) - Contract address
• slot (`0x${string}`) - Storage slot

Returns: Promise<`0x${string}`>

call

Executes a read-only call to a contract.

const result = await adapter.call({
  to: '0x...',
  data: '0x...'
})

• txParams (CallParameters) - Transaction parameters
• provider (PublicClient) - Optional provider override

Returns: Promise<string>

readContract

Reads from a contract function.

const result = await adapter.readContract({
  address: '0x...',
  abi: contractAbi,
  functionName: 'balanceOf',
  args: ['0x...']
})

• address (string) - Contract address
• abi (Abi) - Contract ABI
• functionName (string) - Function to call
• args (unknown[]) - Function arguments
• provider (PublicClient) - Optional provider override

Returns: Promise<unknown>

getBlock

Returns block information for a given block tag.

const block = await adapter.getBlock('latest')

• blockTag (BlockTag) - Block identifier
• provider (PublicClient) - Optional provider override

Returns: Promise<Block>

getContract

Creates a contract instance with a compatible interface.

const contract = adapter.getContract('0x...', contractAbi)
const result = await contract.read.functionName()

• address (string) - Contract address
• abi (Abi) - Contract ABI

Returns: GenericContract

setSigner

Sets or updates the signer for the adapter.

const newAccount = privateKeyToAccount('0x...')
adapter.setSigner(newAccount)

• signer (Account | PrivateKey | WalletClient) - New signer

setProvider

Sets or updates the provider for the adapter.

const newProvider = createPublicClient({ chain: mainnet, transport: http() })
adapter.setProvider(newProvider)

• provider (PublicClient) - New provider

signerOrNull

Returns the signer adapter or null if not set.

const signer = adapter.signerOrNull()
if (signer) {
  // Use signer
}

Returns: ViemSignerAdapter | null

createSigner

Creates a new signer adapter from an account or private key.

const signerAdapter = adapter.createSigner(account)

• signer (Account | PrivateKey | WalletClient) - Signer source

Returns: ViemSignerAdapter

Usage Examples

With Wagmi

import { useWalletClient, usePublicClient } from 'wagmi'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'

function MyComponent() {
  const publicClient = usePublicClient()
  const { data: walletClient } = useWalletClient()

  const adapter = new ViemAdapter({
    provider: publicClient,
    walletClient: walletClient
  })

  // Use adapter with SDK
}

With Private Key

import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { http, createPublicClient, privateKeyToAccount } from 'viem'
import { mainnet } from 'viem/chains'

const account = privateKeyToAccount('0x...')
const provider = createPublicClient({
  chain: mainnet,
  transport: http('https://eth.llamarpc.com')
})

const adapter = new ViemAdapter({ provider, signer: account })

With CoW SDK

import { CowSdk, SupportedChainId } from '@cowprotocol/cow-sdk'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { http, createPublicClient, privateKeyToAccount } from 'viem'
import { sepolia } from 'viem/chains'

const account = privateKeyToAccount('YOUR_PRIVATE_KEY' as `0x${string}`)
const transport = http('YOUR_RPC_URL')
const provider = createPublicClient({ chain: sepolia, transport })
const adapter = new ViemAdapter({ provider, signer: account })

const sdk = new CowSdk({
  chainId: SupportedChainId.SEPOLIA,
  adapter,
  tradingOptions: {
    traderParams: {
      appCode: 'YOUR_APP_CODE',
    },
    options: {
      chainId: SupportedChainId.SEPOLIA,
    },
  },
})

const orderId = await sdk.trading.postSwapOrder(/* ... */)

See Also

• Ethers v5 Adapter
• TradingSdk