pass more than enough arguments to lib/pq

Question

To simplify the code, and prevent from passing similar arguments again and again, I created a method Put for some structures as below.
For example, the reason why UID is not used here is because UID was set as an auto increase value.

type User struct {
    UID      int
    Name     string
    Username string
    Password string
}

func (user *User) Put(db *sql.DB, query string) (sql.Result, error) {
    return db.Exec(query, u.UID, u.Name, u.Username, u.Password)
}

func main() {
    db := ...
    u := &User{...}

    u.Put(db, `INSERT INTO user(name, username, password) VALUES ($2, $3, $4);`)
}

But I get the error below

pq: could not determine data type of parameter $1

(SQL driver is https://github.com/lib/pq)

Answer 1

In your query $2, $3...$N is the index of the argument that is passed in as extra arguments to db.Exec() and they must start from $1(if you use database/sql package).

I think in your case you may to change Put method signature (add struct values extractor)

func (user *User) Put(db *sql.DB, query string, extractor func(user User)[]interface{}) (sql.Result, error) {
    return db.Exec(query, extractor(*user)...)
}

and use one like

u.Put(db,`INSERT INTO user(name, username, password) VALUES ($1, $2, $3);`, func(u User) []interface{} {
    return []interface{}{u.Name, u.Username, u.Password}
})