I've come across a case which is new to me in go. I think it is something similar to this question Idiomatic way to embed struct with custom MarshalJSON() method
Here is an example of code that I am trying to apply
main.go
package main
import (
"context"
"fmt"
"os"
"github.com/ethereum/go-ethereum/ethclient"
)
func main() {
icpPath, _ := os.LookupEnv("GETH_ICP_PATH")
client, _ := ethclient.Dial(icpPath)
ctx := context.Background()
header, _ := client.HeaderByNumber(ctx, nil)
data, _ := header.MarshalJSON()
fmt.Println(string(data))
}
output
{"parentHash":"0x0000000000000000000000000000000000000000000000000000000000000000","sha3Uncles":"0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347","miner":"0x0000000000000000000000000000000000000000","stateRoot":"0xd7f8974fb5ac78d9ac099b9ad5018bedc2ce0a72dad1827a1709da30580f0544","transactionsRoot":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421","receiptsRoot":"0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421","logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","difficulty":"0x400000000","number":"0x0","gasLimit":"0x1388","gasUsed":"0x0","timestamp":"0x0","extraData":"0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa","mixHash":"0x0000000000000000000000000000000000000000000000000000000000000000","nonce":"0x0000000000000042","baseFeePerGas":null,"hash":"0xd4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3"}
In this output for example the field "difficulty"
has a value of "0x400000000"
I can marshal this field like this:
difficulty, _ := header.Difficulty.MarshalJSON()
fmt.Println(string(difficulty))
and get the following output
17179869184
the type of header
is as defined here
https://github.com/ethereum/go-ethereum/blob/master/core/types/block.go
// Header represents a block header in the Ethereum blockchain.
type Header struct {
ParentHash common.Hash `json:"parentHash" gencodec:"required"`
UncleHash common.Hash `json:"sha3Uncles" gencodec:"required"`
Coinbase common.Address `json:"miner" gencodec:"required"`
Root common.Hash `json:"stateRoot" gencodec:"required"`
TxHash common.Hash `json:"transactionsRoot" gencodec:"required"`
ReceiptHash common.Hash `json:"receiptsRoot" gencodec:"required"`
Bloom Bloom `json:"logsBloom" gencodec:"required"`
Difficulty *big.Int `json:"difficulty" gencodec:"required"`
Number *big.Int `json:"number" gencodec:"required"`
GasLimit uint64 `json:"gasLimit" gencodec:"required"`
GasUsed uint64 `json:"gasUsed" gencodec:"required"`
Time uint64 `json:"timestamp" gencodec:"required"`
Extra []byte `json:"extraData" gencodec:"required"`
MixDigest common.Hash `json:"mixHash"`
Nonce BlockNonce `json:"nonce"`
// BaseFee was added by EIP-1559 and is ignored in legacy headers.
BaseFee *big.Int `json:"baseFeePerGas" rlp:"optional"`
}
My question is:
What is the right way to get the json output completly marshaled without going in iterative way through all fields?
CodePudding user response:
The types.Header
type implements a custom json marshaler here, and as you can see it replaces Difficulty *big.Int
with Difficulty *hexutil.Big
which is why you get that hex value in the json.
To disable the custom marshaler you can declare a new type using types.Header
as the type definition, and then, just before you marshal the header, you convert it to this new type.
h := types.Header{Difficulty: big.NewInt(17179869184)}
type MyHeader types.Header // declare new type
out, err := json.Marshal(MyHeader(h)) // convert & marshal