mymap), slices by pointer (&myslice)I keep forgetting that maps are like interfaces in Go, but not slices. You don’t need to dereference a map at all. But you do need to dereference a slice if you want to make changes to it’s underlying array.
package main
import "fmt"
type Loc struct {
X int
Y int
}
var Map = map[string]Loc{}
func Update(a map[string]Loc) {
a[`some`] = Loc{3, 4}
}
func main() {
fmt.Println(Map)
Update(Map)
fmt.Println(Map)
}
Produces:
$ go run /tmp/foo.go
map[]
map[some:{3 4}]
And for slices…
package main
import "fmt"
func BorkUpdate(a []string) {
a = append(a, `some`)
}
func Update(a *[]string) {
(*a) = append((*a), `some`)
}
func main() {
one := []string{`one`}
fmt.Println(one)
Update(one)
fmt.Println(one)
}
Produces:
$ go run /tmp/foo.go
[one]
[one]
[one some]