Gorm Preload data from interface given in func

I have the following structs:

type User struct {
  gorm.Model
  Username string
  Orders   []Order
}

type Order struct {
  gorm.Model
  UserID uint
  Price  float64
}

And try to load the rows from the database with a helper function:

// Return collection of resources
func LoadRows(dest interface{}) error {
  db.Preload("Orders").Find(&dest)
  // [...]
  return fiber.jSON([...])
}

Now I want to load all Users with the orders preloaded:

func main() {
  response := LoadRows([]User);
}

All I get are the users without the preloaded orders. There is also no query in the console that loads the orders. When I change the LoadRows function to the following, everything is working as expected. But then I can not load data in a flexible way:

// Return collection of resources
func LoadRows(dest interface{}) error {
  var result []User // This is needed, otherwise orders are not loaded
  db.Preload("Orders").Find(&result)

  // Now data includes users and orders.
  // [...]
  return fiber.jSON([...])
}

The document you expected this should be explained

https://gorm.io/docs/preload.html

Expected answer

Is it possible to load data with relations in a flexible way or do I always have to set the exact type I want to load?

Comment From: a631807682

Is it possible to load data with relations in a flexible way or do I always have to set the exact type I want to load?

You have to set the exact type, either via generics or via reflect.