Update
Since I'm not able to achieve this using the approach in this question, I created my own library to do the same thing (link). It doesn't rely on go-ethereum package but use the normal net/http
package to do JSON RPC request.
I still love to know what I did wrong in my approach below.
Definitions:
public
variable in contract with address
typeThis is the curl request to get the owner of a contract. I managed to get the owner. (JSON RPC docs)
curl localhost:8545 -X POST \
--header 'Content-type: application/json' \
--data '{"jsonrpc":"2.0", "method":"eth_call", "params":[{"to": "0x_MY_CONTRACT_ADDRESS", "data": "0x8da5cb5b"}, "latest"], "id":1}'
{"jsonrpc":"2.0","id":1,"result":"0x000000000000000000000000_OWNER"}
But when I try to replicate it in Golang (code below), I got json: cannot unmarshal string into Go value of type main.response error. (go-ethereum code that I use)
package main
import (
"fmt"
"log"
"os"
"github.com/ethereum/go-ethereum/rpc"
)
func main() {
client, err := rpc.DialHTTP(os.Getenv("RPC_SERVER"))
if err != nil {
log.Fatal(err)
}
defer client.Close()
type request struct {
To string `json:"to"`
Data string `json:"data"`
}
type response struct {
Result string
}
req := request{"0x_MY_CONTRACT_ADDRESS", "0x8da5cb5b"}
var resp response
if err := client.Call(&resp, "eth_call", req, "latest"); err != nil {
log.Fatal(err)
}
fmt.Printf("%v\n", resp)
}
What did I miss here?
Expected result:
Address in string format. E.g. 0x3ab17372b25154400738C04B04f755321bB5a94b
P/S — I'm aware of abigen and I know it's better and easier to do this using abigen. But I'm trying to solve this specific issue without using abigen method.
You can solve the problem best using the go-ethereum/ethclient:
package main
import (
"context"
"log"
"github.com/ethereum/go-ethereum"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/ethclient"
)
func main() {
client, _ := ethclient.Dial("https://mainnet.infura.io")
defer client.Close()
contractAddr := common.HexToAddress("0xCc13Fc627EFfd6E35D2D2706Ea3C4D7396c610ea")
callMsg := ethereum.CallMsg{
To: &contractAddr,
Data: common.FromHex("0x8da5cb5b"),
}
res, err := client.CallContract(context.Background(), callMsg, nil)
if err != nil {
log.Fatalf("Error calling contract: %v", err)
}
log.Printf("Owner: %s", common.BytesToAddress(res).Hex())
}