如何在go中編組嵌入式結構？

我遇到了一個對我來說很陌生的案例。我認為這類似于這個問題Idiomatic way to embed struct with custom MarshalJSON() method

這是我嘗試應用的代碼示例

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))

}

輸出

{"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"}

例如，在此輸出中，該欄位"difficulty" 的值為"0x400000000"

我可以像這樣編組這個欄位：

difficulty, _ := header.Difficulty.MarshalJSON()
fmt.Println(string(difficulty))

并獲得以下輸出

17179869184

的型別header定義為這里 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"`
}

我的問題是：

在不以迭代方式遍歷所有欄位的情況下，將 json 輸出完全編組的正確方法是什么？

uj5u.com熱心網友回復：

該types.Header型別在此處實作了一個自定義 json 封送拆收器，正如您所看到的，它替換Difficulty *big.Int為Difficulty *hexutil.Big這就是為什么您在 json 中獲得該十六進制值的原因。

要禁用自定義封送拆收器，您可以使用types.Headeras type definition宣告一個新型別，然后，就在您封送標頭之前，將其轉換為這個新型別。

h := types.Header{Difficulty: big.NewInt(17179869184)}

type MyHeader types.Header // declare new type
out, err := json.Marshal(MyHeader(h)) // convert & marshal

https://play.golang.org/p/8CtWWDeItbO

標籤：json 走 编组

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