Go Language: Arrays are passed by value

Unlike other languages, Array are passed by value in Go.

For example, if you call updateCountries method by passing an array as argument, the changes done for the array ‘countries’ inside the method ‘updateCountries’ is not reflected outside.

func updateCountries(countries [5]string) {

    countries[0] = "Dummy"

    countries[1] = "Dummy"

    countries[2] = "Dummy"

    countries[3] = "Dummy"

    countries[4] = "Dummy"

}

App.go

package main

import "fmt"

func main() {
    countries := [5]string{}

    countries[0] = "India"
    countries[1] = "Bangladesh"
    countries[2] = "Canada"
    countries[3] = "Austria"
    countries[4] = "Germany"

    fmt.Println(countries)

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

    updateCountries(countries)

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

func updateCountries(countries [5]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

[India Bangladesh Canada Austria Germany]

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Go Language: Arrays

Array is a collection that stores elements of same type.

Syntax

arrayame := [size]dataType{}

Example

countries := [5]string{}

Above statement defines an array of strings of size 5. ‘countries’ can able to store 5 strings.

HelloWorld.go

package main

import "fmt"

func main() {
 countries := [5]string{}

 countries[0] = "India"
 countries[1] = "Bangladesh"

 fmt.Println(countries)
}

Output

[India Bangladesh   ]

One problem with mentioning size to the array is, we can’t insert elements > size of the array.

HelloWorld.go

package main

import "fmt"

func main() {
 countries := [5]string{}

 countries[0] = "India"
 countries[1] = "Bangladesh"
 countries[2] = "Canada"
 countries[3] = "Austria"
 countries[4] = "Germany"

 countries[5] = "Sri lanka"

 fmt.Println(countries)
}

As you see above program, I mentioned size of array as 5, but I am trying to insert 6^th element into the array.

When you run HelloWorld.go program, you will end up in below error.

$ go run HelloWorld.go

# command-line-arguments

./HelloWorld.go:14:11: invalid array index 5 (out of bounds for 5-element array)

Length of the array

You can use ‘len’ function to get the length of the array.

HelloWorld.go

package main

import "fmt"

func main() {
 countries := [5]string{}

 countries[0] = "India"
 countries[1] = "Bangladesh"

 fmt.Println("Array length : ", len(countries))
}

Output

Array length :  5

Note

Once array is defined, its length is fixed, it can't be resized.

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