Help me, pls. How can I write the received data on file? I need write all-data from section_id, modified_by.

rows, err := db.Query("select section_id, modified_by from enrollment where rownum < 5")
    if err != nil {
        fmt.Println("Error running query")
        fmt.Println(err)
        return
    }
    defer rows.Close()

    var section_id string
    var modified_by string
    for cont := true; cont; cont = rows.NextResultSet() {
        for rows.Next() {
            err := rows.Scan(&section_id, &modified_by)
            if err != nil {
                fmt.Println(err)
            }
            fmt.Println(section_id, modified_by)
        }
    }

}

Thank you for any help!

CodePudding user response：

Replace the loop with

f, err := os.Create("data.txt")
if err != nil {
    log.Fatalf("could not open file: %v", err)
}
defer f.Close()

for cont := true; cont; cont = rows.NextResultSet() {
    for rows.Next() {
        err := rows.Scan(&section_id, &modified_by)
        if err != nil {
            fmt.Println(err)
        }
        fmt.Println(section_id, modified_by)
        n, err := f.WriteString(fmt.Sprintf("%s modified %d", modified_by, section_id))
        if err != nil {
            log.Fatalf("could not write to file: %v", err)
        }
        log.Printf("Wrote %d bytes\n", n)
    }
}

You first open a file, check for errors and then in the loop write every row to the file again with error checks in between. See here for more examples.

CodePudding user response：

You can save your data as a beautified json file using json.MarshalIndent.

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"
)

func ToJsonFile(path string, v interface{}) {
    bytes, _ := json.MarshalIndent(v, "", " ")

    if err := ioutil.WriteFile(path, bytes, 0644); err != nil {
        fmt.Println(err)
        panic(err)
    }
    fmt.Println("Saved the data as json file at "   path)
}

type Enrollment struct {
    SectionId  string `json:"section_id"`
    ModifiedBy string `json:"modified_by"`
}

func PersistData() error {
    // implement db here ...
    
    // array to put data together
    var data []*Enrollment

    rows, err := db.Query("select section_id, modified_by from enrollment where rownum < 5")
    if err != nil {
        fmt.Println("Error running query")
        fmt.Println(err)
        return err
    }
    defer rows.Close()

    for cont := true; cont; cont = rows.NextResultSet() {
        for rows.Next() {
            document := &Enrollment{}

            err := rows.Scan(&document.SectionId, &document.ModifiedBy)
            if err != nil {
                fmt.Println(err)
                return err
            }
            data = append(data, document)
            fmt.Println(document.SectionId, document.ModifiedBy)
        }
    }

    // persist data to a json file
    ToJsonFile("DATA.json", data)
    
    return nil
}