Simulate Contract

SimulateContract executes a contract call via eth_call and returns the decoded return value (and optionally revert info). Use it to test state-changing calls or to validate arguments before sending a transaction. Works with both view and write functions.

Import

import (
  "math/big"
  "github.com/ethereum/go-ethereum/common"
  "github.com/ChefBingbong/viem-go/actions/public"
)

Usage

// SimulateContractParameters requires *abi.ABI
parsedABI, _ := abi.Parse(erc20ABI)

result, err := public.SimulateContract(ctx, publicClient, public.SimulateContractParameters{
  Account:      &senderAddr,
  Address:      common.HexToAddress("0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"),
  ABI:         parsedABI,
  FunctionName: "transfer",
  Args:         []any{recipient, big.NewInt(1000)},
  Value:        big.NewInt(0),
})
if err != nil {
  // e.g. execution reverted
  log.Fatal(err)
}
// result.Result is the decoded return value; result.Request can be used for writeContract

Parameters

Account (optional)

• Type: *common.Address
• Default: nil
• Caller address (msg.sender) for the simulation.

Address (required)

• Type: common.Address
• Contract address to call.

ABI (required)

• Type: *abi.ABI
• Contract ABI for encoding calldata and decoding result.

FunctionName (required)

• Type: string
• Function to call (e.g. "transfer", "approve").

Args (optional)

• Type: []any
• Default: nil
• Function arguments in order.

Value (optional)

• Type: *big.Int
• Default: nil
• Wei to send with the call (for payable functions).

BlockNumber / BlockTag (optional)

• Type: *uint64 or BlockTag
• Default: latest
• Block at which to simulate.

StateOverride / BlockOverrides / AccessList (optional)

• StateOverride: override account/contract state for the call.
• BlockOverrides: override block fields.
• AccessList: EIP-2930 access list.

Gas, GasPrice, MaxFeePerGas, MaxPriorityFeePerGas, Nonce (optional)

• Optional tx-style fields for the simulation context.

Return type

• public.SimulateContract returns (*SimulateContractReturnType, error). SimulateContractReturnType has Result (any — decoded return value) and Request (SimulateContractRequest — can be used to build a writeContract call). On revert, returns an error (use abi.DecodeErrorResult to decode revert data). PublicClient.SimulateContract returns ([]any, error) (decoded return values only).

See also

• Reading Contracts — ReadContract (view/pure)
• Writing Contracts — WriteContract after simulating
• ABI Decoding — DecodeErrorResult for revert data
• Estimate Contract Gas — gas estimation