创建数组的组合文字

Question

I want to create a composite literal of arrays of arrays within a struct. Outside of a struct

package main

import "fmt"

func main() {
  x := [...][]string {{"a", "b"}}

  fmt.Printf("%s", x)
}

works. (http://play.golang.org/p/C2RbNnd7LL)

But I can't define a field of type [...][]string within a struct. As in http://play.golang.org/p/wHNeeuAJuO

package main

import "fmt"

type t struct {
    f    [...][]string
}

func main() {
  x := [...][]string {{"a", "b"}}
  y := t{x}
  fmt.Printf("%s", y)
}

f gives the errror use of [...] array outside of array literal

Answer 1

The problem is that [...]elementType is not a valid type name. You can use the syntax with the initialiser syntax like [...]int{1, 2, 3, 4} because the compiler can see how many elements there are to determine the actual type ([4]int in this case).

If you want an array-like type that doesn't have a fixed compile time size, use a slice:

type t struct {
    f    [][]string
}

Alternatively, if the number of elements is fixed at compile time and you still want to use an array, you will need to specify the actual element count in your type definition.