golang create tree from mysql

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golang web develop always using tree menu in our project.then that can be Reference resources.this article teach you how to get tree menu in web project.

1.show table of menu in mysql database

```mysql> desc menu;+-------+-------------+------+-----+---------+-------+| Field | Type        | Null | Key | Default | Extra |+-------+-------------+------+-----+---------+-------+| id    | int(11)     | YES  |     | NULL    |       || name  | varchar(50) | YES  |     | NULL    |       || pid   | int(11)     | YES  |     | NULL    |       |+-------+-------------+------+-----+---------+-------+3 rows in set (0.00 sec)

```mysql> select * from menu;+------+------+------+| id   | name | pid  |+------+------+------+|    1 | aa   |    0 ||    2 | bb   |    1 ||    3 | cc   |    1 ||    4 | dd   |    2 ||    5 | ee   |    3 ||    6 | ee   |    4 |+------+------+------+6 rows in set (0.00 sec)```

2.base operation in golang,that include tree files thats call db.go/menu.go/main.go

db.gopackage modelimport (    "database/sql"    "fmt"    _ "github.com/go-sql-driver/mysql")var (    dbURL = "root:root@tcp(127.0.0.1:3306)/test?charset=utf8")func Tx(v_sql string, args ...interface{}) (*sql.Rows, error) {    db, err := sql.Open("mysql", dbURL)    defer db.Close()    stmt, err := db.Prepare(v_sql)    if err != nil {        fmt.Println("Tx err:", err)        return nil, err    }    return stmt.Query(args...)}

menu.gopackage modelimport (    "database/sql"    "fmt")const (    QuerySQL = "select id,name,pid from menu where pid =?")type Menu struct {    CurId    int64   `json:"curid"`    Name     string  `json:"name"`    ParentId int64   `json:"parentid"`    Child    []*Menu `json:"child,omitempty"`}func MenuAppend(m *Menu) {    fmt.Println(QuerySQL)    child, err := MenuInit(QuerySQL, m.CurId)    if err != nil {        fmt.Println("MenuAppend err:", err)        return    }    m.Child = child    for _, v := range m.Child {        MenuAppend(v)    }}func LoadMenu() (*Menu, error) {    ms, err := MenuInit(QuerySQL, 0)    if err != nil {        fmt.Println("LoadMenu err:", err)        return nil, err    }    root := ms[0]    MenuAppend(root)    return root, nil}func MenuInit(sql0 string, id int64) ([]*Menu, error) {    rows, err := Tx(sql0, id)    if err != nil {        fmt.Println("MeneInit err:", err)        return nil, err    }    ms := make([]*Menu, 0)    for rows.Next() {        m := &Menu{}        var id sql.NullInt64        var name sql.NullString        var pid sql.NullInt64        if err = rows.Scan(&id, &name, &pid); err != nil {            fmt.Println("MenuInit error:", err)            return nil, err        }        if id.Valid {            m.CurId = id.Int64        }        if name.Valid {            m.Name = name.String        }        if pid.Valid {            m.ParentId = pid.Int64        }        ms = append(ms, m)    }    fmt.Println("current data:", ms)    return ms, nil}

main.gopackage mainimport (    "encoding/json"    "fmt"    _ "github.com/go-sql-driver/mysql"    "model")func main() {    root, err := model.LoadMenu()    if err != nil {        fmt.Println("err:", err)    }    b, err := json.Marshal(root)    fmt.Println(string(b))}

3.run and get tree data from json

{  "curid": 1,   "name": "aa",   "parentid": 0,   "child": [    {      "curid": 2,       "name": "bb",       "parentid": 1,       "child": [        {          "curid": 4,           "name": "dd",           "parentid": 2,           "child": [            {              "curid": 6,               "name": "ee",               "parentid": 4            }          ]        }      ]    },     {      "curid": 3,       "name": "cc",       "parentid": 1,       "child": [        {          "curid": 5,           "name": "ee",           "parentid": 3        }      ]    }  ]}