How to create an array of struct arrays of different types?

In my program I got 2 models:

type User struct {
    Name string
}

type Article struct {
    Title string
}

And I got arrays of data of these structs:

users := []User
articles := []Article

I'm trying to iterate over both of them at the same piece of code:

models := [][]interface{} {users, articles}
for _, model := range models {
    log.Printf("%#v", model)
}

But I'm receiving an error:

cannot use users (type []User) as type []interface {} in array element

What am I doing wrong?

You should use []interface{} instead of [][]interface{}
Try it on the <kbd>go playground</kbd>

If you want to iterate all structs in your inner arrays, you need to cast them to the proper type and then iterate, like this:

for _, model := range models {
	if u, ok := model.([]User); ok {
		for _, innerUser := range u {
			log.Printf("%#v", innerUser)
		}
	}
	if a, ok := model.([]Article); ok {
		for _, innerArticle := range a {
			log.Printf("%#v", innerArticle)
		}
	}
}

Try it on the <kbd>go playground</kbd>

Maybe I'm not getting your requirements, but what's wrong with just

models := []interface{} {users, articles}
for _, model := range models {
    log.Printf("%#v\n", model)
}

How about using interfaces to solve your problem? you can even use the default fmt.Stringer interface, used by fmt.Prtinf and other standard methods.

Example:

package main

import "log"
import "fmt"

type User struct {
	Name string
}

type Article struct {
	Title string
}

func (art Article) String() string {
	return art.Title
}

func (user User) String() string {
	return user.Name
}

func main() {
	models := []interface{}{User{"user1"}, User{"user2"}, Article{"article1"}, Article{"article2"}}
	for _, model := range models {
		printable := model.(fmt.Stringer)
		log.Printf("%s\n", printable)
	}
}

Playground: https://play.golang.org/p/W3qakrMfOd