Go: declaring a slice inside a struct?

Question

I have the following code:

type room struct {
    width float32
    length float32
}
type house struct{
    s := make([]string, 3)
    name string
    roomSzSlice := make([]room, 3)
} 

func main() {


}

And when i try to build and run it i get the following errors:

c:\go\src\test\main.go:10: syntax error: unexpected :=
c:\go\src\test\main.go:11: non-declaration statement outside function body
c:\go\src\test\main.go:12: non-declaration statement outside function body
c:\go\src\test\main.go:13: syntax error: unexpected }

What did i do wrong?

Thanks!

Answer 1

You can declare a slice in a struct declaration, but you can not initialize it. You have to do this by different means.

// Keep in mind that lowercase identifiers are
// not exported and hence are inaccessible
type House struct {
    s []string
    name string
    rooms []room
}

// So you need accessors or getters as below, for example
func(h *House) Rooms()[]room{
    return h.rooms
}

// Since your fields are inaccessible, 
// you need to create a "constructor"
func NewHouse(name string) *House{
    return &House{
        name: name,
        s: make([]string, 3),
        rooms: make([]room, 3),
    }
}

Please see the above as a runnable example on Go Playground

---

EDIT

To Initialize the struct partially, as requested in the comments, one can simply change

func NewHouse(name string) *House{
    return &House{
        name: name,
    }
}

Please see the above as a runnable example on Go Playground, again

Answer 2

First off you cannot assign/initialize inside the struct. The := operator declares and assigns. You can however, achieve the same result simply.

Here is a simple, trivial example that would do roughly what you're trying:

type house struct {
    s []string
}

func main() {
    h := house{}
    a := make([]string, 3)
    h.s = a
}

I've never written one that way, but if it servers your purpose... it compiles anyway.