> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cow.bleu.builders/llms.txt
> Use this file to discover all available pages before exploring further.

# Viem Adapter

> Integration between the CoW Protocol SDK and the Viem library

# Viem Adapter

The Viem Adapter provides integration with the [viem](https://viem.sh) library, enabling you to use all CoW Protocol SDK packages with viem clients and accounts.

## Installation

```shellscript theme={null}
npm install @cowprotocol/sdk-viem-adapter
```

## Constructor

```typescript theme={null}
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

<ResponseField name="provider" type="PublicClient" required>
  A viem `createPublicClient` instance
</ResponseField>

<ResponseField name="signer" type="Account | `0x${string}`">
  A viem account from `privateKeyToAccount` or similar
</ResponseField>

<ResponseField name="walletClient" type="WalletClient">
  A viem WalletClient, useful with wagmi's `useWalletClient` hook
</ResponseField>

## Properties

### signer

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

```typescript theme={null}
const signerAdapter = adapter.signer
```

### utils

Utility methods for working with viem types and contracts.

```typescript theme={null}
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.

```typescript theme={null}
const chainId = await adapter.getChainId()
```

Returns: `Promise<number>`

### getCode

Returns the bytecode at a given address.

```typescript theme={null}
const code = await adapter.getCode('0x...')
```

* `address` (`string`) - Contract address

Returns: `Promise<string | undefined>`

### getTransactionReceipt

Returns the transaction receipt for a given transaction hash.

```typescript theme={null}
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.

```typescript theme={null}
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.

```typescript theme={null}
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.

```typescript theme={null}
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.

```typescript theme={null}
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.

```typescript theme={null}
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.

```typescript theme={null}
const newAccount = privateKeyToAccount('0x...')
adapter.setSigner(newAccount)
```

* `signer` (`Account | PrivateKey | WalletClient`) - New signer

### setProvider

Sets or updates the provider for the adapter.

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

* `provider` (`PublicClient`) - New provider

### signerOrNull

Returns the signer adapter or null if not set.

```typescript theme={null}
const signer = adapter.signerOrNull()
if (signer) {
  // Use signer
}
```

Returns: `ViemSignerAdapter | null`

### createSigner

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

```typescript theme={null}
const signerAdapter = adapter.createSigner(account)
```

* `signer` (`Account | PrivateKey | WalletClient`) - Signer source

Returns: `ViemSignerAdapter`

## Usage Examples

### With Wagmi

```typescript theme={null}
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

```typescript theme={null}
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

```typescript theme={null}
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](/cow-sdk/api/adapters/ethers-v5)
* [TradingSdk](/cow-sdk/api/trading-sdk)