Problem initializing nested structs

[Jason Gu]

Hi,

I've having trouble trying to initialize a struct with an embedded struct:

package game

type Config struct {
  Size struct{ w, h int }
  Gravity float64
  speed int
}

package main

func main() {

   config := game.Config{
      Size: struct{ w, h int }{ w: 800, h: 600 }, // Error: Cannot use struct{ w, h int }{ w: 800, h: 600 } (type struct {...}) as type struct {...} 
   }
}

I understand I can make "Size" an exported type in package game and that would work.

I'd like to know why can't I use struct literal for initialization; is it because the struct in (Size struct{ w, h int }) is an unnamed type and unnamed types are never exported?

[pierre...@gmail.com]

Hello,

The reason is that the fields of the anonymous struct are not exported.

The error message actually mentions it:

"cannot use struct { w int; h int } literal (type struct { w int; h int }) as type struct { game.w int; game.h int } in field value"

Exporting those makes the program compile.

HTH

[Miguel Angel Rivera Notararigo]

This works for me, just export the struct fields.

$GOPATH/test/main.go:

package main


import (
  "fmt"

  "test/game"
)

func main() {
  config := game.Config{

    Size: struct{ W, H int }{W: 800, H: 600},
  }
 
  fmt.Println(config)
}

$GOPATH/test/game/game.go:

package game


type Config struct {

  Size    struct{ W, H int }
  Gravity float64
  speed   int
}

[Jason Gu]

Thanks! exporting the fields worked :)