R - Define a object in a function which is inside another function

Question

I have one function inside another like this:

func2 <- function(x=1) {ko+x+1}
func3= function(l=1){
  ko=2
  func2(2)+l
}
func3(1)

it shows error: Error in func2(2) : object 'ko' not found. Basically I want to use object ko in func2 which will not be define until func3 is called. Is there any fix for this?

Answer 1

Yes, it can be fixed:

func2 <- function(x=1) {ko+x+1}
func3= function(l=1){
  ko=2
  assign("ko", ko, environment(func2))
  res <- func2(2)+l
  rm("ko", envir = environment(func2))
  res
}
func3(1)
#[1] 6

As you see this is pretty complicated. That's often a sign that you are not following good practice. Good practice would be to pass ko as a parameter:

func2 <- function(x=1, ko) {ko+x+1}
func3= function(l=1){
  ko=2
  func2(2, ko)+l
}
func3(1)
#[1] 6

Answer 2

You don't really have one function "inside" the other currently (you are just calling a function within a different function). If you did move the one function inside the other function, then this would work

func3 <- function(l=1) {
  func2 <- function(x=1) {ko+x+1}
  ko <- 2
  func2(2)+l
}
func3(1)

Functions retain information about the environment in which they were defined. This is called "lexical scoping" and it's how R operates.

But in general I agree with @Roland that it's better to write functions that have explicit arguments.