> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/cowprotocol/cow-sdk/llms.txt
> Use this file to discover all available pages before exploring further.

# Viem Adapter

> Integration adapter for using the CoW Protocol SDK with 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

```bash 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

<ParamField path="provider" type="PublicClient" required>
  A viem PublicClient instance created with `createPublicClient`.
</ParamField>

<ParamField path="signer" type="Account | PrivateKey">
  Optional viem account instance or private key string. Can be created with `privateKeyToAccount` or obtained from wagmi hooks.
</ParamField>

<ParamField path="walletClient" type="WalletClient">
  Optional WalletClient instance. Use this instead of `signer` when working with wagmi's `useWalletClient` hook.
</ParamField>

## 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 interface = 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...')
```

**Parameters:**

* `address` (string): The 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...')
```

**Parameters:**

* `hash` (string): The 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')
```

**Parameters:**

* `address` (Address): The contract address
* `slot` (`0x${string}`): The 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...'
})
```

**Parameters:**

* `txParams` (TransactionParams): Transaction parameters
* `provider` (PublicClient, optional): Override provider

**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...']
})
```

**Parameters:**

* `address` (string): Contract address
* `abi` (Abi): Contract ABI
* `functionName` (string): Function name to call
* `args` (ContractValue\[], optional): Function arguments
* `provider` (PublicClient, optional): Override provider

**Returns:** `Promise<unknown>`

### getBlock

Returns block information for a given block tag.

```typescript theme={null}
const block = await adapter.getBlock('latest')
```

**Parameters:**

* `blockTag` (BlockTag): Block tag (e.g., 'latest', 'pending', block number)
* `provider` (PublicClient, optional): Override provider

**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()
```

**Parameters:**

* `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)
```

**Parameters:**

* `signer` (Account | PrivateKey): New signer to use

### setProvider

Sets or updates the provider for the adapter.

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

**Parameters:**

* `provider` (PublicClient): New provider to use

**Returns:** `PublicClient`

### 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)
```

**Parameters:**

* `signer` (Account | PrivateKey | ViemSignerAdapter): Signer to wrap

**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(parameters)
```

## See Also

* [Viem Documentation](https://viem.sh)
* [Ethers v6 Adapter](/api/adapters/ethers-v6)
* [Ethers v5 Adapter](/api/adapters/ethers-v5)