reflect.IsNil() Function in Golang with Examples

Go language provides inbuilt support implementation of run-time reflection and allowing a program to manipulate objects with arbitrary types with the help of reflect package. The reflect.IsNil() Function in Golang is used to check whether its argument v is nil. The argument must be a chan, func, interface, map, pointer, or slice value; if it is not, IsNil panics.

Note: IsNil is not always equivalent to a regular comparison with nil in Go. For example, if v was created by calling ValueOf with an uninitialized interface variable i, i==nil will be true but v.IsNil will panic as v will be the zero Value.

Syntax:

func (v Value) IsNil() bool

Parameters: This function does not accept any parameter.

Return Value: This function returns whether its argument v is nil or not.

Below examples illustrate the use of above method in Golang:

Example 1:

// Golang program to illustrate
// reflect.IsNil() Function

package main

import (
    "bytes"
    "fmt"
)

// Main function
func main() {
    var body *bytes.Buffer
    fmt.Printf("main(): body == nil ? %t\n", body == nil)
}

Output:

main(): body == nil ? true

Example 2:

// Golang program to illustrate
// reflect.IsNil() Function

package main

import (
    "fmt"
    "reflect"
)

func isNilFixed(i interface{}) bool {
   if i == nil {
      return true
   }
   switch reflect.TypeOf(i).Kind() {
   case reflect.Ptr, reflect.Map, reflect.Array, reflect.Chan, reflect.Slice:
    //use of IsNil method
    return reflect.ValueOf(i).IsNil()
   }
   return false
}

// Main function
func main() {
    t := reflect.TypeOf(5)

    arr := reflect.ArrayOf(4, t)
    inst := reflect.New(arr).Interface().(*[4]int)

    for i := 1; i <= 4; i++ {
        inst[i-1] = i*i
    }

    fmt.Println(isNilFixed(inst))
}

Output:

false