Appending to a slice

It is common to append new elements to a slice, and so Go provides a built-in append function. The documentation of the built-in package describes append. 

  1. func append(s []T, vs ...T) []T

The first parameter s of append is a slice of type T, and the rest are T values to append to the slice.

The resulting value of append is a slice containing all the elements of the original slice plus the provided values.

If the backing array of s is too small to fit all the given values a bigger array will be allocated. The returned slice will point to the newly allocated array.

(To learn more about slices, read the Slices: usage and internals article.)

append.go

  1. package main
  3. import "fmt"
  5. func main() {
  6.     var s []int
  7.     printSlice(s)
  9.     // append works on nil slices.
  10.     s = append(s, 0)
  11.     printSlice(s)
  13.     // The slice grows as needed.
  14.     s = append(s, 1)
  15.     printSlice(s)
  17.     // We can add more than one element at a time.
  18.     s = append(s, 2, 3, 4)
  19.     printSlice(s)
  20. }
  22. func printSlice(s []int) {
  23.     fmt.Printf("len=%d cap=%d %v\n", len(s), cap(s), s)
  24. }