simulateCalls

Simulates a set of calls for a block, and optionally provides asset changes. Internally uses the eth_simulateV1 JSON-RPC method.

Usage

import {  } from 'viem'
import {  } from './config'
 
const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [
    {
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },
    {
      : '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
      : ('1'),
    },
  ],
})
 
.()
]

Contract Calls

The calls property also accepts Contract Calls, and can be used via the abi, functionName, and args properties.

import { ,  } from 'viem'
import {  } from './config'
 
const  = ([
  'function mint()',
  'function transfer(address, uint256) returns (bool)',
])
 
const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [
    {
      : '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
      : ('1')
    },
    {
      : '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
      ,
      : 'mint',
    },
    {
      : '0x95aD61b0a150d79219dCF64E1E6Cc01f0B64C4cE',
      ,
      : 'transfer',
      : [
        '0xa5cc3c03994DB5b0d9A5eEdD10CabaB0813678AC',
        100n
      ],
    },
  ],
})
 
.()
]

Asset Changes

Providing the traceAssetChanges parameter (with an account) will return asset balance changes for the calls.

import { ,  } from 'viem'
import {  } from './config'
 
const  = ([
  'function mint()',
  'function transfer(address, uint256) returns (bool)',
])
 
const { ,  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [
    {
      : '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
      : ('1.5')
    },
    {
      : '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
      ,
      : 'mint',
    },
    {
      : '0x95aD61b0a150d79219dCF64E1E6Cc01f0B64C4cE',
      ,
      : 'transfer',
      : [
        '0xa5cc3c03994DB5b0d9A5eEdD10CabaB0813678AC',
        100n
      ],
    },
  ],
  : true, 
})
 
.()
]

Reading Contracts

It is also worth noting that simulateCalls also supports "reading" contracts.

import {  } from 'viem'
import {  } from './config'
 
const  = ([
  'function totalSupply() returns (uint256)',
  'function ownerOf(uint256) returns (address)',
])
 
const {  } = await .({
  : [
    {
      : '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
      ,
      : 'totalSupply',
    },
    {
      : '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
      ,
      : 'ownerOf',
      : [69420n],
    },
    {
      : '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
      ,
      : 'ownerOf',
      : [13371337n],
    },
  ],
})
 
.()
]

Return Value

SimulateCallsReturnType

Simulation results.

Parameters

calls

Type: Calls

Calls to simulate.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D', 
      : ('2'), 
    }, 
    { 
      : '0x70997970c51812dc3a010c7d01b50e0d17dc79c8', 
      : ('1'), 
    }, 
  ], 
})

calls.data

Type: Hex

Calldata to broadcast (typically a contract function selector with encoded arguments, or contract deployment bytecode).

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xdeadbeef', 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D', 
      : ('2'), 
    },  
  ], 
})

calls.to

Type: Address

The recipient address.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D', 
      : ('2'),
    },  
  ], 
})

calls.value

Type: Address

Value to send with the call.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'), 
    },  
  ], 
})

calls.dataSuffix

Type: Hex

Data to append to the end of the calldata.

example.ts

// @filename: config.ts
import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'
 
export const client = createPublicClient({
  chain: mainnet,
  transport: http(),
})
// @filename: example.ts
// ---cut---
import { parseAbi } from 'viem'
import { client } from './config'
 
const abi = parseAbi([
  'function approve(address, uint256) returns (bool)',
])
 // ---cut---
const { id } = await client.simulateCalls({
  calls: [
    {
      to: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2',
      abi,
      functionName: 'approve',
      args: [
        '0xa5cc3c03994DB5b0d9A5eEdD10CabaB0813678AC', 
        100n
      ],
      dataSuffix: '0xdeadbeef'
    }
  ],
})

account (optional)

Type: Account | Address

The account to simulate the calls from.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929', 
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
})

blockNumber (optional)

Type: bigint

The block number to simulate the calls at.

const {  } = await .({
  : 17030000n, 
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
})

blockTag (optional)

Type: BlockTag

The block tag to simulate the calls at.

const {  } = await .({
  : 'pending', 
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
})

stateOverrides (optional)

Type: StateOverride

The state overrides to simulate the calls with.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
  : [{ 
    : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929', 
    : ('10000'), 
  }], 
})

traceAssetChanges (optional)

Type: boolean

Whether to trace asset changes.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
  : true, 
})

traceTransfers (optional)

Type: boolean

Whether to trace transfers.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
  : true, 
})

validation (optional)

Type: boolean

Whether to enable validation mode.

const {  } = await .({
  : '0x5a0b54d5dc17e482fe8b0bdca5320161b95fb929',
  : [ 
    { 
      : '0xcb98643b8786950F0461f3B0edf99D88F274574D',
      : ('2'),
    },  
  ], 
  : true, 
})

Suggest changes to this page