包装函数； 返回函数的函数

Question

I am not sure how to write a wrapper function for something that includes magrittr pipe (%>%). I am trying to create a wrapper function that returns addPolyline() , addPolygon() or addCircleMarkers() depending on the layer type but I have not been successful. It seems the answer will be in Hadley's Advanced material but most likely it went over my head. As a simple example, how can I make something like the following example work:

library(leaflet)

wrapper <- function() {
  myfunc <- function() {addPolylines(data = leaflet::atlStorms2005)}
  return(myfunc)
}

# I want this
leaflet() %>% addTiles() %>% addPolylines(data = leaflet::atlStorms2005)

# but I need a wrapper function
leaflet() %>% addTiles() %>% wrapper()

Answer 1

It seems that you need to modify your wrapper function a little and use %>% wrapper()() in the pipe.

library(leaflet)

wrapper <- function() {
    myfunc <- function(.) {addPolylines(., data = leaflet::atlStorms2005)}
    return(myfunc)
}

# I want this
leaflet() %>% addTiles() %>% addPolylines(data = leaflet::atlStorms2005)

# but I need a wrapper function
leaflet() %>% addTiles() %>% wrapper()()

Answer 2

It doesn't seem like you need a function that returns a function. You just need a function that can call other functions.

wrapper <- function(x) {
  x %>% addPolylines(data = leaflet::atlStorms2005)
}

leaflet() %>% addTiles() %>% wrapper()