Go language: Slices are passed by reference

In Go language, Arrays are passed by value, whereas slices are passed by reference.

func updateCountries(countries []string) {

    countries[0] = "Dummy"

    countries[1] = "Dummy"

    countries[2] = "Dummy"

    countries[3] = "Dummy"

    countries[4] = "Dummy"

}

For example, if you call updateCountries method by passing a slice as an argument, the changes done for the slice ‘countries’ inside the method ‘updateCountries’ will be reflected outside.

App.go

package main

import "fmt"

func main() {
    countries := []string{}

    countries = append(countries, "India")
    countries = append(countries, "Bangladesh")
    countries = append(countries, "Canada")
    countries = append(countries, "Austria")
    countries = append(countries, "Germany")

    fmt.Println(countries)

    fmt.Println("\nUpdating countries with Dummy data")

    updateCountries(countries)

    fmt.Println()
    fmt.Println(countries)
}

func updateCountries(countries []string) {
    countries[0] = "Dummy"
    countries[1] = "Dummy"
    countries[2] = "Dummy"
    countries[3] = "Dummy"
    countries[4] = "Dummy"
}

Output

[India Bangladesh Canada Austria Germany]

Updating countries with Dummy data

[Dummy Dummy Dummy Dummy Dummy]

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Go Language: Arrays vs slices

a.   Arrays are fixed in size. If you create an array of size 6, then it can able to store exactly 6 elements. You can’t store more than 6 elements in the array, but slices can be resized on demand.

b.   Slices are built on top of arrays. If you are changing any value of the slice, then it is going to change the value of underlying array and vice versa.

c.    Arrays are passed by value, whereas slices are passed by reference.

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