结合公众号小店做网站ebay欧洲站网址

背景

在Fabric链码中，我们可以使用PutState方法对一个key的值进行覆盖，当我们再使用GetState查询时是最新的值。如果我们希望找到这个key的修改记录，我们可以使用溯源方法GetHistoryForKey。完整源码链接：https://github.com/hyperledger/fabric-samples/blob/main/asset-transfer-ledger-queries/chaincode-go/asset_transfer_ledger_chaincode.go

代码

// HistoryQueryResult structure used for returning result of history query
type HistoryQueryResult struct {Record    *Asset    `json:"record"`TxId      string    `json:"txId"`Timestamp time.Time `json:"timestamp"`IsDelete  bool      `json:"isDelete"`
}// GetAssetHistory returns the chain of custody for an asset since issuance.
func (t *SimpleChaincode) GetAssetHistory(ctx contractapi.TransactionContextInterface, assetID string) ([]HistoryQueryResult, error) {log.Printf("GetAssetHistory: ID %v", assetID)resultsIterator, err := ctx.GetStub().GetHistoryForKey(assetID)if err != nil {return nil, err}defer resultsIterator.Close()var records []HistoryQueryResultfor resultsIterator.HasNext() {response, err := resultsIterator.Next()if err != nil {return nil, err}var asset Assetif len(response.Value) > 0 {err = json.Unmarshal(response.Value, &asset)if err != nil {return nil, err}} else {asset = Asset{ID: assetID,}}timestamp, err := ptypes.Timestamp(response.Timestamp)if err != nil {return nil, err}record := HistoryQueryResult{TxId:      response.TxId,Timestamp: timestamp,Record:    &asset,IsDelete:  response.IsDelete,}records = append(records, record)}return records, nil
}