Go Empty Interface

We know that interfaces are used to store a set of methods without implementation. In Go, we can also create interfaces without any methods, known as empty interfaces. For example,

interface {}

Here, we have created an empty interface without any methods.

Variable of Empty Interface in Golang

In Go, we can create variables of the empty interface type. For example,

package main
import "fmt"

func main() {

  // variable of empty interface type
  var a interface {}
  fmt.Println("Value:", a)

}

Output

Value: <nil>

Here, we have created a variable of type empty interface. When we print the variable, we get nil as output.

Empty Interface to Pass Function Argument of Any Type

Normally in functions, when we pass values to the function parameters, we need to specify the data type of parameters in a function definition.

However, with an empty interface, we can pass parameters of any data type. For example,

package main
import "fmt"

// empty interface as function parameter
func displayValue(i interface {}) {
  fmt.Println(i)
}

func main() {

  a := "Welcome to Programiz"
  b := 20
  c := false

  // pass string to the function 
  displayValue(a)

  // pass integer number to the function
  displayValue(b)

  // pass boolean value to the function
  displayValue(c)

}

Output

Welcome to Programiz
20
false

In the above example, we have used an empty interface i as the parameter to the displayValue() function.

Now the same function works for any type of parameters (string,numeric, boolean).

Go Empty Interface to Pass Any Numbers of Arguments

We can also use an empty interface to pass any number of arguments to the function definition. For example,

package main
import "fmt"

// function with an empty interface as its parameter
func displayValue(i... interface {}) {
  fmt.Println(i)
}

func main() {

  a := "Welcome to Programiz"
  b := 20
  c := false

  // function call with a single parameter
  displayValue(a)

  // function call with 2 parameters
  displayValue(a, b)

  // function call with 3 parameters
  displayValue(a, b, c)

}

Output

[Welcome to Programiz 20 false 20 40 Hi again]

In the above example, we have used an empty interface i as the parameter to the displayValue() function.

func displayValue(i... interface{})

Now the same function works for any number of parameters.