I have something like the following type structure below:
type Set []*Element
func (set *Set) AppendElements(elements []*Elements) {
// ?
}
Obviously simply appending elements to a slice is not very useful. However, the actual function takes some value, does some business logic, and then appends the elements. However, I am facing the difficulty that modifications to the slice inside of the method to not actually change the value of the slice to outside callers, because the append method allocates a new slice that is not seen by the callers.
Is there a way to append to the slice in a method or should the slice be wrapped in a struct or something else?
package main
import "fmt"
type Element int
type Set []*Element
func (ptr *Set) AppendElements(elements []*Element) {
set := *ptr
set = append(set, elements...)
}
func main() {
i := Element(1)
var set Set
set.AppendElements([]*Element{&i})
for _, el := range set {
fmt.Println(el)
}
}
More specifically, the above prints nothing.
You're modifying the slice, but you never assign it back to the pointer.
func (ptr *Set) AppendElements(elements []*Element) {
set := *ptr
set = append(set, elements...)
*ptr = set
}
Usually though, one would dereference the pointer directly in the append statement:
func (set *Set) AppendElements(elements []*Element) {
*set = append(*set, elements...)
}