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writeContract

Calls a write function on a contract.

A "write" function on a Solidity contract modifies the state of the blockchain. These types of functions require gas to be executed, and hence a Transaction is needed to be broadcast in order to change the state.

Internally, writeContract uses a Wallet Client to call the sendTransaction action with ABI-encoded data.

Import

ts
import { writeContract } from 'viem'

Usage

Below is a very basic example of how to call a write function on a contract (with no arguments).

ts
import { writeContract } from 'viem'
import { walletClient } from './client'
import { wagmiAbi } from './abi'

await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
})
ts
export const wagmiAbi = [
  ...
  {
    inputs: [],
    name: "mint",
    outputs: [],
    stateMutability: "nonpayable",
    type: "function",
  },
  ...
] as const;
ts
import { createWalletClient, custom } from 'viem'
import { mainnet } from 'viem/chains'

export const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

Passing Arguments

If your function requires argument(s), you can pass them through with the args attribute.

TypeScript types for args will be inferred from the function name & ABI, to guard you from inserting the wrong values.

For example, the mint function name below requires a tokenId argument, and it is typed as [number].

ts
import { writeContract } from 'viem'
import { walletClient } from './client'
import { wagmiAbi } from './abi'

await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420]
})
ts
export const wagmiAbi = [
  ...
  {
    inputs: [{ internalType: "uint32", name: "tokenId", type: "uint32" }],
    name: "mint",
    outputs: [],
    stateMutability: "nonpayable",
    type: "function",
  },
  ...
] as const;
ts
import { createWalletClient, custom } from 'viem'
import { mainnet } from 'viem/chains'

export const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

Return Value

Hash

A Transaction Hash.

Unlike readContract, writeContract only returns a Transaction Hash. If you would like to retrieve the return data of a write function, you can use the callContract action – this action does not execute a transaction, and does not require gas (it is very similar to readContract).

Parameters

address

  • Type: Address

The contract address.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', 
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420]
})

abi

The contract's ABI.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi, 
  functionName: 'mint',
  args: [69420]
})

functionName

  • Type: string

A function to extract from the ABI.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint', 
  args: [69420]
})

accessList (optional)

The access list.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  accessList: [{ 
    address: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266',
    storageKeys: ['0x1'],
  }], 
})

args (optional)

  • Type: Inferred from ABI.

Arguments to pass to function call.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420] 
})

from (optional)

  • Type: Address

Optional sender override.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  from: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' 
})

gasPrice (optional)

  • Type: bigint

The price (in wei) to pay per gas. Only applies to Legacy Transactions.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  gasPrice: parseGwei('20'), 
})

maxFeePerGas (optional)

  • Type: bigint

Total fee per gas (in wei), inclusive of maxPriorityFeePerGas. Only applies to EIP-1559 Transactions

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  maxFeePerGas: parseGwei('20'),  
})

maxPriorityFeePerGas (optional)

  • Type: bigint

Max priority fee per gas (in wei). Only applies to EIP-1559 Transactions

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  maxFeePerGas: parseGwei('20'),
  maxPriorityFeePerGas: parseGwei('2'), 
})

nonce (optional)

  • Type: number

Unique number identifying this transaction.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  nonce: 69 
})

value (optional)

  • Type: number

Value in wei sent with this transaction.

ts
await writeContract(walletClient, {
  address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
  abi: wagmiAbi,
  functionName: 'mint',
  args: [69420],
  value: parseEther('1') 
})

Released under the MIT License.

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