Snippet

Encapsulating state within closures

A closure is a function value that references variables from outside its body. In Go, returning a function that references a local variable binds the variable to that instance of the function, creating encapsulated state without using explicit struct objects.

snippet.go

package main
 
import "fmt"
 
func newCounter() func() int {
	count := 0
	return func() int {
		count++
		return count
	}
}
 
func main() {
	counter := newCounter()
	fmt.Println(counter())
	fmt.Println(counter())
	
	anotherCounter := newCounter()
	fmt.Println(anotherCounter())
}

Breakdown

func newCounter() func() int {

Defines a higher-order function that returns another function returning an int.

count := 0

Declares a local variable whose scope is extended because it is captured by the returned closure.

return func() int {

Returns the anonymous inner function (closure) that modifies and reads the outer variable.

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Encapsulating state within closures

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