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import GoDocLink from '../components/godoc' import EIPLink from '../components/eip' import {Address, ABI} from '../components/primitives'

Contract

The Contract struct represents a deployed Solidity contract.

To instantiate a Contract object use:

contract.NewContract(addr, abi)

with:

  • addr : Address of the contract.
  • abi : ABI of the contract.

By default, it connects to the https://localhost:8545 JsonRPC endpoint.

Options

Besides addr and abi, you can use the option pattern to parametrize the contract, the available options are:

  • WithJsonRPCEndpoint: JsonRPC url of the endpoint to connect with.
  • WithJsonRPCClient: JsonRPC object to make rpc calls. It takes preference over an address from WithAddress.
  • WithSigner: Signer object to send transactions or use a custom from address.
  • WithProvider: Custom NodeProvider implementation to resolve calls and transactions.
  • WithEIP1559: Send transactions with EIP-1559 pricing.

Examples

Check examples for a list of examples on how to interact with a smart contract.

Call a contract

package main

import (
	"fmt"
	"math/big"

	"github.com/umbracle/ethgo"
	"github.com/umbracle/ethgo/abi"
	"github.com/umbracle/ethgo/contract"
	"github.com/umbracle/ethgo/jsonrpc"
)

func handleErr(err error) {
	if err != nil {
		panic(err)
	}
}

// call a contract
func main() {
	var functions = []string{
		"function totalSupply() view returns (uint256)",
	}

	abiContract, err := abi.NewABIFromList(functions)
	handleErr(err)

	// Matic token
	addr := ethgo.HexToAddress("0x7d1afa7b718fb893db30a3abc0cfc608aacfebb0")

	client, err := jsonrpc.NewClient("https://mainnet.infura.io")
	handleErr(err)

	c := contract.NewContract(addr, abiContract, contract.WithJsonRPC(client.Eth()))
	res, err := c.Call("totalSupply", ethgo.Latest)
	handleErr(err)

	fmt.Printf("TotalSupply: %s", res["totalSupply"].(*big.Int))
}

Abigen

One small limitation of Contract is that works with interface objects since the input and outputs of a smart contract are arbitrary. As an alternative, you can use Abigen to generate Go bindings that wrap the Contract object and provide native and typed Go functions to interact with the contracts.

By default, ethgo includes builtin abigen contracts for ens and erc20 tokens.