function as a return value, don't understand the output of an example

Zoya 0
Viewed 46

The following example prints 12. I can't understand this output. Why did it print 12 and not 11?

func fA() func() int {
    i := 0
    return func() int {
        i++
        return i
    }
}
func main() {
   fB := fA()
   fmt.Print(fB())
   fmt.Print(fB())
}
go
1 Answers

It is a closure. Basically, the function returned knows the variable defined outside its scope, so when you call fA(), the returned function has i = 0, when you call fB(), it increments the value of i, now i = 1. when you call it again it will increment i again, and now you have i = 2. If you create a new function using fA(), this new function will have a new i. Something like this:

 fB := fA()
 fC := fA()
 fmt.Print(fB())// 1
 fmt.Print(fB())// 2
 fmt.Print(fC())// 1
 fmt.Print(fB())// 3
Akami0
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