22_deferring_function_calls.go

package main

import (
	"fmt"
)

/*
-Go's "defer" statement does exactly what it says. It defers execution of a block of
 code until everything else in the current function is finished
-Each time you call the "defer" statement, it adds an instruction to a stack and when the
 deferred statements are executed, they' re handled in last in first out order, known as LIFO
*/

func main() {
	// defer statement runs "fmt.Println("Close the file!")" after everything else
	// is finished in this function -- because this is the first one deferred
	defer fmt.Println("Close the file!")
	fmt.Println("Open the file!")

	defer fmt.Println("Statement 1")
	defer fmt.Println("Statement 2")

	// the defer keyword only works within a function.
	// any deferred statements will be executed at the end of the current function,
	// rather than waiting for the entire application
	myFunc()

	defer fmt.Println("Statement 3")
	defer fmt.Println("Statement 4")
	fmt.Println("Undeferred statment")

	// any values that you refer to in a deferred statement
	// is evaluated at the moment that the statement is deferred
	// rather than when it's executed

	x := 1000
	defer fmt.Println("Value of x:", x) // this will print 1000 as the value of x because of the reason above
	x++
	fmt.Println("Value of x after incrementing", x)
}

func myFunc() {
	defer fmt.Println("Deffered in the function")
	fmt.Println("Not deferred in the function")
}