复制具有基本类型的interface {}参数

Question

I am populating lists of structs from a postgres database using the native sql library and jmoiron/sqlx. I currently have separate functions for different types, for example:

func selectAccounts(ext sqlx.Ext, query string, args []interface{}) ([]Account, error) {
    var accts []Account
    rows, err := ext.Queryx(query, args...)
    if err != nil {
        return nil, err
    }
    defer rows.Close()

    for rows.Next() {
        var a Account
        if err = rows.StructScan(&a); err != nil {
            return nil, err
        }
        accts = append(accts, a)
    }
    err = rows.Err()
    return accts, err
}

... but I have a requirement to build a generic function that accepts interface{} and returns a []interface{}. I am finding the process of replacing the line var a Account above is difficult, as it requires making a copies of the passed in interface{} type while replicating its underlying type. Should I resign myself to the fact that I need to be using reflection, or is there another way to go about doing this?

Answer 1

Couldn't you make your structs polymorphic and have them implement a single interface? Then your function can return a slice of said interface? This way you wouldn't have to use reflection. I was thinking something along these lines:

package main

import (
    "fmt"
)

type Account interface {
    GetDetails() string
}

type PersonAccount struct {
    Name string
}

func NewPersonAccount(name string) Account {
    return &PersonAccount{
        Name: name,
    }
}

func (account *PersonAccount) GetDetails() string {
    return account.Name
}

type BillingAccount struct {
    AccountNumber string
}

func NewBillingAccount(accountNumber string) Account {
    return &BillingAccount{
        AccountNumber: accountNumber,
    }
}

func (account *BillingAccount) GetDetails() string {
    return account.AccountNumber
}

func getAllAccounts() []Account {
    accounts := make([]Account, 0)
    accounts = append(accounts, NewPersonAccount("John Doe"))
    accounts = append(accounts, NewBillingAccount("1234-5678"))

    return accounts
}

func main() {
    accounts := getAllAccounts()

    for _, account := range accounts {
        fmt.Println(account.GetDetails())
    }
}

/* Output:
John Doe
1234-5678
*/