ABI Introduction

Contract ABI: using a parsed ABI for encoding and decoding contract calls, events, and errors in viem-go

This section covers contract-level ABI usage: encoding function calldata, event topics, and errors, and decoding function results and event logs using a parsed ABI. To get a parsed ABI, use abi.Parse(jsonABI) — see Parse ABI for full parsing docs.

Import

import (
  "encoding/hex"
  "github.com/ChefBingbong/viem-go/abi"
  "github.com/ethereum/go-ethereum/common"
)

ABI type

After parsing, you get an ABI struct:

Field	Type	Description
Functions	`map[string]Function`	Function name → definition.
Events	`map[string]Event`	Event name → definition.
Errors	`map[string]Error`	Error name → definition.

Helper methods:

*GethABI() abi.ABI — underlying go-ethereum ABI.
Raw() []byte — original JSON bytes.
HasFunction(name string) bool
HasEvent(name string) bool
FunctionNames() []string
EventNames() []string

Function type

Each Function has:

Name — function name.
Inputs — []Parameter (name, type, components for tuples).
Outputs — []Parameter.
StateMutability — Pure, View, NonPayable, Payable.
Selector — [4]byte (first 4 bytes of keccak256(signature)).
Signature — e.g. "transfer(address,uint256)".
IsReadOnly() bool — true for Pure/View.

Event type

Each Event has:

Name — event name.
Inputs — []Parameter (each may be Indexed).
Anonymous — whether the event is anonymous.
Topic — common.Hash (keccak256 of event signature).
Signature — e.g. "Transfer(address,address,uint256)".

Error type

Each Error has:

Name — error name.
Inputs — []Parameter.
Selector — [4]byte (first 4 bytes of keccak256(signature)).
Signature — e.g. "InsufficientBalance(uint256,uint256)".

Parameter type

Parameter (used in function/event/error inputs/outputs):

Name — parameter name.
Type — Solidity type string (e.g. "address", "uint256", "tuple").
Indexed — for events, whether the parameter is indexed.
Components — for tuple types, nested parameters.

State mutability

Constants: Pure, View, NonPayable, Payable. Use ParseStateMutability(s string) to parse a string.

Go notes

The ABI struct is built from go-ethereum’s parser; MarshalJSON / UnmarshalJSON are implemented so the ABI can be serialized as the original JSON.