KITFORMA · EDITORIAL GUIDE
Why does editing a struct range variable leave my Go slice unchanged?
KitForma editorial guide. A range value can be a copy of the element. Editing that local struct does not necessarily replace the stored element.
Step-by-step guidance
A range value can be a copy of the element. Editing that local struct does not necessarily replace the stored element.
Use indexes when mutating actual slice elements, or assign a modified copy back explicitly:
package main
import "fmt"
type item struct { Count int }
func main() {
items := []item{{Count: 1}}
for i := range items { items[i].Count++ }
fmt.Println(items[0].Count)
}Expected output is 2. Test the collection afterward, not just the loop variable. A slice of pointers has different sharing behavior. Index-based mutation also does not make simultaneous access by other goroutines safe.
Sources and verification
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