golang: convert row sql to object

Question

Hello I am using pgx to use my postgres, and I have doubts as to how I can transform a row in the database into an aggregate

I am using entities and value objects without value object it seems easy using marshal, but using value object I think it is not a good idea to have fields exported and then my question comes in, how can I convert my line into a struct of my aggregate

my aggregrate :

type Email struct {
    address string
}

type Password struct {
    value string
}

type Name struct {
    firstName string
    lastName  string
}

type Person struct {
    Id       string
    Name     valueObject.Name
    Email    valueObject.Email
    Password valueObject.Password
    Created  time.Time
    Updated  time.Time
}

func NewPerson(name valueObject.Name, email valueObject.Email, password valueObject.Password) *Person {
    id := uuid.New()
    return &Person{
        Id:       id.String(),
        Name:     name,
        Email:    email,
        Password: password,
        Created:  time.Now(),
        Updated:  time.Now(),
    }
}

all my value objects have a method to get the private value through a function simulating a get, I didn’t put the rest of the code of my value objects so it wouldn’t get big

func to get all rows from table:

func (r *personRepository) GetAll() (persons []*entities.Person, err error) {
    qry := `select id, first_name, last_name, email, password created_at, updated_at from persons`
    rows, err := r.conn.Query(context.Background(), qry)

    return nil, fmt.Errorf("err")
}

If someone can give me a glimpse of how I can pass this line from the bank to a struct of my aggregate using this value object

ישו אוהב אותך · Accepted Answer · 2021-04-26 05:14:49Z

1

You can use something like this (not yet tested and need optimization):

func (r *personRepository) GetAll() (persons []*entities.Person, err error) {
    qry := `select id, first_name, last_name, email, password, created_at, updated_at from persons`
    rows, err := r.conn.Query(context.Background(), qry)

  var items []*entities.Person
  if err != nil {
    // No result found with the query.
    if err == pgx.ErrNoRows {
        return items, nil
    }
    
    // Error happened
    log.Printf("can't get list person: %v\n", err)
    return items, err
  }

  defer rows.Close()

  for rows.Next() {
    // Build item Person for earch row.
    // must be the same with the query column position.

    var id, firstName, lastName, email, password string
    var createdAt, updatedAt time.Time
    
    err = rows.Scan(&id, &firstName, &lastName, &email,
                    &createdAt, updatedAt)
    if err != nil {
        log.Printf("Failed to build item: %v\n", err)
        return items, err
    }

    item := &entities.Person{
      Id: id,
      FirstName: firstName,
      // fill other value
    }

    // Add item to the list.
    items = append(items, item)
  }

  return items, nil
}

Don't forget to add the comma after text password in your query.

I am using entities and value objects without value object it seems easy using marshal,

Sorry, I don't know about the value object in your question.

answered Apr 26, 2021 at 5:14

ישו אוהב אותך

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3 Comments

Ming Over a year ago

I can only create a valuable object, like password, name, by a like constructor NewPassword (p string), NewEmail (and string) why the fields of my structs of my value objects are not exported

ישו אוהב אותך Over a year ago

You need to uppercase the first character of your fields to make it exportable.

Ming Over a year ago

I understand, but that way I would lose the sense of using valuables, I was trying to see if I had an alternative to making the marshal with non-exported fields.

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