The Zero Value Nil in Golang

1. Check the Size of nil With Different Types in Golang
2. Return nil String in Golang

nil is a zero value in the Go programming language, a well-known and significant predefined identifier. It is the literal representation of several different types of zero values.

Many novice Go programmers who have worked in other popular languages may consider nil the equivalent of null (or NULL) in other languages. This is partially correct, but there are several distinctions between nil in Go and null (or NULL) in other languages.

We’ll look at a few instances to see what nil means in Golang.

Check the Size of nil With Different Types in Golang

The memory layouts of all types of values are always the same. The type’s nil values are not exceptions (assume zero value as nil).

A nil value’s size is always the same as the sizes of non-nil values with the same type as the nil value. However, nil values of various types may have different sizes.

Code:

package main

import (
	"fmt"
	"unsafe"
)

func main() {
	var p *struct{} = nil
	fmt.Println(unsafe.Sizeof(p))

	var s []int = nil
	fmt.Println(unsafe.Sizeof(s))

	var m map[int]bool = nil
	fmt.Println(unsafe.Sizeof(m))

	var c chan string = nil
	fmt.Println(unsafe.Sizeof(c))

	var f func() = nil
	fmt.Println(unsafe.Sizeof(f))

	var i interface{} = nil
	fmt.Println(unsafe.Sizeof(i))
}

Output:

8
24
8
8
8
16

Return nil String in Golang

The pointer variable type that refers to a string value is string. A pointer’s zero value is nil.

Code:

package main

import (
	"fmt"
)

func main() {
	var data *string = nil
	if data == nil {
		fmt.Println(data)
	}
}

Output:

<nil>

In this following example, we will check if nil == nil in Golang.

Code:

package main

import (
	"fmt"
)

func main() {
	var i *int = nil
	var j *int = nil
	if i == j {
		fmt.Println("equal")
	} else {
		fmt.Println("no")
	}
}

Output:

equal