Is it possible to pass leaflet map to another module? - r

Question

I write an app which I try to modularize. In general, I added leaflet map to my app's body (in main module) and what I want to do is to write some other modules which refer to my main map (showing/hiding points on a map and other spatial operations). I try to refer to this map (being in main module) from other modules. In example below I passed map as reactive expression from main module but when I press button showing points on the map then the error shows up:
Error in if: missing value where TRUE/FALSE needed
Is it possible to pass map to another module at all? And use leafletProxy there?
Here is reproducible example:
library(shiny)
library(dplyr)
library(sf)
library(leaflet)
moduleServer <- function(id, module) {
callModule(module, id)
}
# Main module - UI 1 #
mod_btn_UI1 <- function(id) {
ns <- NS(id)
tagList(
leafletOutput(ns("map")),
mod_btn_UI2(ns("other"))
)
}
# Main module - Server 1 #
mod_btn_server1 <- function(id){
moduleServer(id, function(input, output, session) {
ns <- NS(id)
# here I pass map as reactive
passMap = reactive({input$map})
coords <- quakes %>%
sf::st_as_sf(coords = c("long","lat"), crs = 4326)
output$map <- leaflet::renderLeaflet({
leaflet::leaflet() %>%
leaflet::addTiles() %>%
leaflet::setView(172.972965,-35.377261, zoom = 4) %>%
leaflet::addCircleMarkers(
data = coords,
stroke = FALSE,
radius = 6)
})
mod_btn_server2("other", passMap)
})
}
# Other module - UI 2 #
mod_btn_UI2 <- function(id) {
ns <- NS(id)
tagList(
actionButton(inputId = ns("btn"), label = "show points")
)
}
# Other module - Server 2 #
mod_btn_server2 <- function(id, passMap){
moduleServer(id, function(input, output, session) {
ns <- NS(id)
coords <- quakes %>%
sf::st_as_sf(coords = c("long","lat"), crs = 4326)
observeEvent(input$btn, {
leaflet::leafletProxy(passMap()) %>%
leaflet::addCircleMarkers(
data = coords,
stroke = TRUE,
color = "red",
radius = 6)
})
})
}
# Final app #
ui <- fluidPage(
tagList(
mod_btn_UI1("test-btn"))
)
server <- function(input, output, session) {
mod_btn_server1("test-btn")
}
shinyApp(ui = ui, server = server)

Answer 1

It seems that you need to pass down the leaflet proxy as a reactive to the module for it to work.
Added a leaflet proxy instead of input name for the variable passMap in module mod_btn_server1:
proxymap <- reactive(leafletProxy('map'))
mod_btn_server2("other", proxymap)
In mod_btn_server2 you have then to change Passmap to be the leafletproxy itself removing the call to leafletproxy:
observeEvent(input$btn, {
passMap() %>%
leaflet::addCircleMarkers(
data = coords,
stroke = TRUE,
color = "red",
radius = 6)
})
The full code here:
library(shiny)
library(dplyr)
library(sf)
library(leaflet)
moduleServer <- function(id, module) {
callModule(module, id)
}
# Main module - UI 1 #
mod_btn_UI1 <- function(id) {
ns <- NS(id)
tagList(
leafletOutput(ns("map")),
mod_btn_UI2(ns("other"))
)
}
# Main module - Server 1 #
mod_btn_server1 <- function(id){
moduleServer(id, function(input, output, session) {
ns <- NS(id)
# here I pass map as reactive
passMap = reactive({input$map})
coords <- quakes %>%
sf::st_as_sf(coords = c("long","lat"), crs = 4326)
output$map <- leaflet::renderLeaflet({
leaflet::leaflet() %>%
leaflet::addTiles() %>%
leaflet::setView(172.972965,-35.377261, zoom = 4) %>%
leaflet::addCircleMarkers(
data = coords,
stroke = FALSE,
radius = 6)
})
proxymap <- reactive(leafletProxy('map'))
mod_btn_server2("other", proxymap)
})
}
# Other module - UI 2 #
mod_btn_UI2 <- function(id) {
ns <- NS(id)
tagList(
actionButton(inputId = ns("btn"), label = "show points")
)
}
# Other module - Server 2 #
mod_btn_server2 <- function(id, passMap){
moduleServer(id, function(input, output, session) {
ns <- NS(id)
coords <- quakes %>%
sf::st_as_sf(coords = c("long","lat"), crs = 4326)
observeEvent(input$btn, {
passMap() %>%
leaflet::addCircleMarkers(
data = coords,
stroke = TRUE,
color = "red",
radius = 6)
})
})
}
# Final app #
ui <- fluidPage(
tagList(
mod_btn_UI1("test-btn"))
)
server <- function(input, output, session) {
mod_btn_server1("test-btn")
}
shinyApp(ui = ui, server = server)