Anonymous functions
Go language provides a special feature known as an anonymous function.
An anonymous function is a function which doesn’t contain any name. It is useful when you want to create an inline function. In Go language, an anonymous function can form a closure. An anonymous function is also known as function literal.
Go playground: https://go.dev/play/p/oRvkptTza2q.
Examples
Example with pointer
type Example struct {
Name *string
}
func NewExampleLong() Example {
name := "example"
return Example{
Name: &name,
}
}
func NewExample() Example {
return Example{
// Anonymous function
Name: func() *string {
n := "example"
return &n
}(),
}
}
This can be annoying when you have a lot of parameters, of course you can use pointer function libraries like https://github.com/AlekSi/pointer. But here, the goal is simply to use fewer variables to avoid confusion.
Go playground: https://go.dev/play/p/EKd55TFq0Eb.
Example with if
type Example struct {
Name *string
Example2 string
}
func NewExample2Long(example bool) Example {
if example {
return Example{
Example2: "if example",
// Anonymous function
Name: func() *string {
n := "example"
return &n
}(),
}
}
return Example{
Example2: "else example",
// Anonymous function
Name: func() *string {
n := "example"
return &n
}(),
}
}
func NewExample2(example bool) Example {
return Example{
// Anonymous function
Example2: func() string {
if example {
return "if example"
}
return "else example"
}(),
// Anonymous function
Name: func() *string {
n := "example"
return &n
}(),
}
}
In that case, it’s very useful and avoid copy past of your struct definition.
Go playground: https://go.dev/play/p/AnxvcLhOBdN.
Example with a variable
func main() {
// Anonymous function
example3 := func() {
fmt.Println("Hi A Trick A Day !")
}
example3()
example3()
example3()
}
In Go language, you are allowed to assign an anonymous function to a variable. When you assign a function to a variable, then the type of the variable is of function type and you can call that variable like a function call as shown in the above example.
Go playground: https://go.dev/play/p/RYPHKySpCEc.
Example with parameters
func main() {
example := "Hi A Trick A Day !"
// Anonymous function
func() {
fmt.Println(example)
}()
// Anonymous function
func(s string) {
fmt.Println(s)
}("Hi A Trick A Day !")
}
You can also pass arguments into the anonymous function. Preferably reuse variables from your main function and use parameters when you have references like loop variables.
Go playground: https://go.dev/play/p/B9LueTouvmc.