Converting Log Topics to int64 correctly in Go

Question

I currently use the code below to extract the ERC721 Token ID from Transfer Event Logs:

txHash := newLog.TxHash.Hex()
hexString := common.BytesToAddress(newLog.Topics[3].Bytes()).Hex()
flowerNum, _ := strconv.ParseUint(hexString, 0, 10)
flowerNumInt := int64(flowerNum)

flowerNumInt is 1023, even though txHash linked below references FLOWER #1133. Moreso, FLOWER #1023 has no transfer events at all, and does not appear in the tx linked below.

https://etherscan.io/tx/0xe330601b05c54116da3b06dd17cf483ab3106fb969989458c8587aac1c34fbf3

Am I doing something wrong during the conversion?

Answer 1

Here's a full example of decoding the log topic to get the value (in your case the ID as an uint64):

package main

import (
    "context"
    "fmt"
    "log"
    "math/big"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/ethclient"
)

func main() {
    client, err := ethclient.Dial("https://mainnet.infura.io")
    if err != nil {
        log.Fatal(err)
    }

    txID := common.HexToHash("0xe330601b05c54116da3b06dd17cf483ab3106fb969989458c8587aac1c34fbf3")
    receipt, err := client.TransactionReceipt(context.Background(), txID)
    if err != nil {
        log.Fatal(err)
    }

    logID := "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
    for _, vLog := range receipt.Logs {
        if vLog.Topics[0].Hex() == logID {
            if len(vLog.Topics) > 2 {
                id := new(big.Int)
                id.SetBytes(vLog.Topics[3].Bytes())

                fmt.Println(id.Uint64()) // 1133
            }
        }
    }
}