Trying to scan into a struct dynamically from SQL

[Monosij Dutta-Roy]

Hello All -

A little new to go and reading from a SQL DBMS and trying to scan into a struct.

I am trying to keep it dynamic in sending a query and scanning into the required struct.

The structs I am using for the entities Member, in this case, I would like to use to read from other DBMS as well such as MongoDB thus do not want to be dependent on sql.NllString.

I understand I may have to use a different library such as sqlx by jmoiron - but wanted to ask first if there is a way to just use the sql package?

...

While I have gotten the following code fragment to work:

rows, err := db.Query("SELECT * FROM member")

PanicIf(err)

cols, err := rows.Columns()

PanicIf(err)

defer rows.Close()

vals := make([]interface{}, len(cols))

for i, _ := range cols {

vals[i] = new(sql.RawBytes)

}

I am trying to get the following part in reading into the struct Member to work:

members := []Member{}

for rows.Next() {

mem := Member{}

err := rows.Scan(vals...) // This works but I cannot get it into the Memeber struct as tried below.

// I want the following to work somehow?

// err := rows.Scan(&mem.ID, &mem.Name, &mem.Description, &mem.Country, &mem.Region)

PanicIf(err)

members = append(members, mem)

Would there be a way to use rows.Scan to scan directly into the Member struct.

...

Member struct is defined as:

type Member struct {

ID int

Name string

Description string

  Country string  // do not want to use sql.NullString as I do not want to make my memeber struct SQL DBMS dependent.

  Region string  // do not want to use sql.NullString as I do not want to make my memeber struct SQL DBMS dependent.

}

...

Thank you for your help!

[Jia Mi]

Hi Monosij,

I'm working on a code generator for accessing RDBMS called ModelQ, although only mysql supported for now. You could check it out at https://github.com/mijia/modelq

The basic idea is after you scan the row into RawBytes you have to process/xform from the RayBytes into your own model object. Like the examples in modelq, scan rows into a User object:

func (o _UserObjs) toUser(columns []gmq.Column, rb []sql.RawBytes) User {

    obj := User{}

    if len(columns) == len(rb) {

        for i := range columns {

            switch columns[i].Name {

            case "id":

                obj.Id = gmq.AsInt64(rb[i])

            case "name":

                obj.Name = gmq.AsString(rb[i])

            case "password":

                obj.Password = gmq.AsString(rb[i])

            case "is_married":

                obj.IsMarried = gmq.AsInt(rb[i])

            case "age":

                obj.Age = gmq.AsInt(rb[i])

            case "create_time":

                obj.CreateTime = gmq.AsTime(rb[i])

            case "update_time":

                obj.UpdateTime = gmq.AsTime(rb[i])

            }

        }

    }

    return obj

}

I think the RawBytes is just the string bytes, so you need to parse it yourself.

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[Monosij Dutta-Roy]

Hi Jia -

Thanks for your reply. This looks great.

I will take a close look at what you are doing. I would like to use aspects of this library.

I got a chance to do what I needed to do for now using sqlx by jMoiron.

I will get back to you in a day or so and if I can contrbute perhaps I can help as well.

Thank you.

Mono

[georgy...@gmail.com]

Hi. I created a library that does exactly that and it's much simpler to use compared to sqlx: https://github.com/georgysavva/scany