Why don't changes made to a struct via a method persist? -

i'm trying understand why following test code not working expected:

package main  import (     "fmt"     "strings" )  type test struct {     somestrings []string }  func (this test) addstring(s string) {     this.somestrings = append(this.somestrings, s)     this.count() // print "1" }  func (this test) count() {     fmt.println(len(this.somestrings)) }  func main() {     var test test     test.addstring("testing")     test.count() // print "0" } 

this print:

"1" "0" 

meaning somestrings apparently modified... , it's not.

anybody know issue?

the addstring method using value (copy) receiver. modification made copy, not original. pointer receiver must used mutate original entity:

package main  import (         "fmt" )  type test struct {         somestrings []string }  func (t *test) addstring(s string) {         t.somestrings = append(t.somestrings, s)         t.count() // print "1" }  func (t test) count() {         fmt.println(len(t.somestrings)) }  func main() {         var test test         test.addstring("testing")         test.count() // print "0" } 

playground

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output

1 1