Golang Anonymous Function

An anonymous refers to a function that does not have a name. This type of function is also known as a function literal or a lambda function in other programming languages.

Go allows you to create in-line or anonymous functions for short-term use as we will show in this tutorial.

Golang Declare Anonymous Function

We can declare an anonymous function in Go the same way we would when declaring a normal function.

For example, the code below creates an anonymous function inside the main function.

package main
import "fmt"
func main() {
func() {
fmt.Println("I don't have a name")
}
}

Golang Invoke Anonymous Function

Once we declare an anonymous function, we can invoke immediately, as shown in the example below:

package main
import "fmt"
func main() {
func() {
fmt.Println("I don't have a name")
}() // invoke func
}

The above code should execute the code inside the anonymous function and return the string as:

$ go run anonymous_functions.go
I don't have a name

Golang Anonymous Function Assign Variable

We can also assign an anonymous function to a variable and call it using the variable name. Consider the example below:

package main
import "fmt"
func main() {
str := func() {
fmt.Println("Hi")
}
str()
}

In the example above, we create a variable called “str” and assign it to an anonymous function. We can the use the variable name to call the function.

Golang Pass Arguments to Anonymous Function

Like a typical function in Go, we can pass any number of arguments (of any type) to an anonymous function as shown in the example code below:

package main
import "fmt"
func main() {
func (a float64) {
fmt.Printf("Result: %f", a*3.141)
}(7.0)
}

In the example above, we pass an argument of type float64 to an anonymous function. Once we call the function, we pass the require argument.

The code above returns:

Result: 21.987000

Golang Return Anonymous Function from Another Function

Go also allows you to return an anonymous function from another function. An example is as shown in the code below:

package main
import "fmt"
func main() {
anon_func := func() func(x int) {
result := func(x int) {
fmt.Println("Result: ", x)
}
return result
}

y := anon_func()
y(2)
}

The above code returns 2.

Conclusion

This guide takes you through the basics of working with anonymous functions in the Go programming language.