Go - append to slice in struct

Question

I am trying to implement 2 simple structs as follows:

package main

import (
    "fmt"
)

type MyBoxItem struct {
    Name string
}

type MyBox struct {
    Items []MyBoxItem
}

func (box *MyBox) AddItem(item MyBoxItem) []MyBoxItem {
    return append(box.Items, item)
}

func main() {

    item1 := MyBoxItem{Name: "Test Item 1"}
    item2 := MyBoxItem{Name: "Test Item 2"}

    items := []MyBoxItem{}
    box := MyBox{items}

    AddItem(box, item1)  // This is where i am stuck

    fmt.Println(len(box.Items))
}

What am i doing wrong? I simply want to call the addItem method on the box struct and pass an item in

question from:https://stackoverflow.com/questions/18042439/go-append-to-slice-in-struct

Answer 1

Hmm... This is the most common mistake that people make when appending to slices in Go. You must assign the result back to slice.

func (box *MyBox) AddItem(item MyBoxItem) []MyBoxItem {
    box.Items = append(box.Items, item)
    return box.Items
}

Also, you have defined AddItem for *MyBox type, so call this method as box.AddItem(item1)