Gorm:如何在字段中存储结构

Question

我正在尝试将*hedera.ContractID类型的hederea合同ID保存到Gorm字段中，但我得到了错误“为struct *hedera.ContractID字段AliasKey:定义关系的有效外键或实现Valuer接口”

包装合同

import (
    "fmt"

    "github.com/.../scanner/controllers/blockchain"
    database "github.com/.../scanner/db"
    model "github.com/.../scanner/models"
    "github.com/rs/xid"
    "gorm.io/gorm"
)

func DeployContract() *gorm.DB {

    //connect to database
    db, err := database.ConnectToDB()

    //if db connection fails
    if err != nil {
        panic(err)
    }

    //init model
    var modelContract model.Contract

    //check if a contract has been deployed
    if err := db.First(&modelContract); err.Error != nil {
        //no deployment found

        //Migrate the schema
        db.AutoMigrate(&model.Contract{})

        //deploy contract
        contract, _ := blockchain.DeployContract()

        //create record

        // generate random id
        id := xid.New()

        // Create
        db.Create(&model.Contract{
            Id:            id.String(),
            ContractId:    contract.Receipt.ContractID,
            GasUsed:       contract.CallResult.GasUsed,
            TransactionId: fmt.Sprint(contract.TransactionID),
            Timestamp:     contract.ConsensusTimestamp,
            ChargeFee:     fmt.Sprint(contract.TransactionFee),
            PayerAccount:  fmt.Sprint(contract.TransactionID.AccountID),
            Status:        fmt.Sprint(contract.Receipt.Status),
        })

    }

    return db
}

Gorm模型

package models

import (
    "time"

    "github.com/hashgraph/hedera-sdk-go/v2"
    "gorm.io/gorm"
)

type Contract struct {
    gorm.Model
    Id            string
    ContractId    *hedera.ContractID
    GasUsed       uint64
    TransactionId string
    Timestamp     time.Time
    ChargeFee     string
    PayerAccount  string
    Status        string
}

Answer 1

对于自定义数据类型，您需要指定如何从数据库存储和检索该值。这是通过实现Scanner和Valuer接口来完成的。

但是，由于hedera.ContractID是在另一个包中定义的，因此需要创建自己的ContractID并实现这些接口。就像这样：

type ContractID hedera.ContractID

type Contract struct {
    gorm.Model
    Id            string
    ContractId    *ContractID
    GasUsed       uint64
    TransactionId string
    Timestamp     time.Time
    ChargeFee     string
    PayerAccount  string
    Status        string
}     

func (c *ContractID) Scan(value interface{}) error {
  bytes, ok := value.([]byte)
  if !ok {
    return errors.New(fmt.Sprint("Failed to unmarshal ContractID value:", value))
  }

  return json.Unmarshal(bytes, c)
}

func (c ContractID) Value() (driver.Value, error) {
  return json.Marshal(c)
}

此外，无论在哪里使用hedera.ContractID，都可以将它转换为model.ContractID。例如：

    cID := model.ContractID(*contract.Receipt.ContractID)

    // Create
    db.Create(&model.Contract{
        Id:            id.String(),
        ContractId:    &cID,
        GasUsed:       contract.CallResult.GasUsed,
        TransactionId: fmt.Sprint(contract.TransactionID),
        Timestamp:     contract.ConsensusTimestamp,
        ChargeFee:     fmt.Sprint(contract.TransactionFee),
        PayerAccount:  fmt.Sprint(contract.TransactionID.AccountID),
        Status:        fmt.Sprint(contract.Receipt.Status),
    })