Gorm: How to store structs in fields

Question content

I tried to save the hederea contract id of *hedera.contractid type into the gorm field, but received the error " is struct github.com/hashgraph/hedera-sdk-go/v2 An invalid field was found. Field aliaskey of accountid: Define a valid foreign key for the relationship or implement the valuer interface”

Packaging Contract

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 model

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
}

Correct answer

For custom data types, you need to specify how the value is stored and retrieved from the database. This is done by implementing the scanner and valuer interfaces.

However, since hedera.contractid is defined in another package, you need to create your own contractid and implement these interfaces. Something like this:

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)
}

Additionally, hedera.contractid is converted to model.contractid wherever used. For example:

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),
    })

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