Create a shiny module that creates a leaflet map

Question

I have the simple shiny app below in which I create a leaflet map. I would like to create a shiny module though that would specifically create the leaflet map.

    ## app.R ##
library(shiny)
library(shinydashboard)
library(shinyWidgets)
library(leaflet)
library(dplyr)

# Some data
data<-structure(list(scientificName = c("Turdus merula Linnaeus, 1758", 
                                        "Passer domesticus (Linnaeus, 1758)", "Cantharellus cinereus (Pers.) Fr.", 
                                        "Flammulina fennae Bas", "Mycena crocata (Schrad.) P.Kumm.", 
                                        "Lepista luscina (Fr.) Singer", "Mycena permixta (Britzelm.) Sacc.", 
                                        "Rhodophyllus byssisedus (Pers.) Quel.", "Rhodophyllus porphyrophaeus (Fr.) J.E.Lange", 
                                        "Panaeolus rickenii Hora"), decimalLatitude = c(52.204429, 51.387818, 
                                                                                        52.176667, 50.066111, 49.179167, 49.419444, 52.3, 52.3, 49.419444, 
                                                                                        49.179167), decimalLongitude = c(21.189275, 19.62673, 19.088056, 
                                                                                                                         19.502778, 22.434722, 20.380556, 20.566667, 20.566667, 20.380556, 
                                                                                                                         22.434722)), row.names = c(1L, 2L, 32L, 35L, 37L, 38L, 39L, 40L, 
                                                                                                                                                    41L, 42L), class = c("spec_tbl_df", "tbl_df", "tbl", "data.frame"
                                                                                                                                                    ))
# Define the side panel UI and server
sideUI <- function(id) {
  ns <- NS(id)
  pickerInput(
    inputId = ns("sci"),
    label = "Scientific name", 
    choices = unique(data$scientificName),
    selected = unique(data$scientificName)[1] 
    
  )
  actionButton("action","Submit")
  
}

sideServer <- function(id) {
  moduleServer(
    id,
    function(input, output, session) {
      
      # define a reactive and return it
      react<-eventReactive(input$action,{
        
        omited <-subset(data, data$scientificName %in% isolate(input$sci))
      })
      return(react)
      
    })
}
# In this case this server not needed but using uiOuput/renderUI in real case
# sideServer <- function(id) { moduleServer(id,function(input, output, session) { })}

# Define the UI and server functions for the map
mapUI <- function(id) {
  ns <- NS(id)
  leafletOutput(ns("map"))
}

mapServer <- function(id, city) {
  moduleServer(
    id,
    function(input, output, session) {
      output$map<-renderLeaflet({
        
        leaflet(data = react()) %>% addTiles() %>%
          addMarkers(~decimalLatitude, ~decimalLongitude, popup = ~as.character(scientificName), label = ~as.character(scientificName))
      })
    })
}

# Build ui & server and then run
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(sideUI("side")),
  dashboardBody(mapUI("mapUK"))
)
server <- function(input, output, session) {
  
  # use the reactive in another module
  city_input <- sideServer("side")
  mapServer("mapUK", city_input)
  
}
shinyApp(ui, server)

Answer 1

You have made some mistakes.

Below is code without these mistakes:

library(shiny)
library(shinydashboard)
library(shinyWidgets)
library(leaflet)
library(dplyr)

# Some data
data<-structure(list(scientificName = c("Turdus merula Linnaeus, 1758", 
                                        "Passer domesticus (Linnaeus, 1758)", "Cantharellus cinereus (Pers.) Fr.", 
                                        "Flammulina fennae Bas", "Mycena crocata (Schrad.) P.Kumm.", 
                                        "Lepista luscina (Fr.) Singer", "Mycena permixta (Britzelm.) Sacc.", 
                                        "Rhodophyllus byssisedus (Pers.) Quel.", "Rhodophyllus porphyrophaeus (Fr.) J.E.Lange", 
                                        "Panaeolus rickenii Hora"), decimalLatitude = c(52.204429, 51.387818, 
                                                                                        52.176667, 50.066111, 49.179167, 49.419444, 52.3, 52.3, 49.419444, 
                                                                                        49.179167), decimalLongitude = c(21.189275, 19.62673, 19.088056, 
                                                                                                                         19.502778, 22.434722, 20.380556, 20.566667, 20.566667, 20.380556, 
                                                                                                                         22.434722)), row.names = c(1L, 2L, 32L, 35L, 37L, 38L, 39L, 40L, 
                                                                                                                                                    41L, 42L), class = c("spec_tbl_df", "tbl_df", "tbl", "data.frame"
                                                                                                                                                    ))
# Define the side panel UI and server
sideUI <- function(id) {
  ns <- NS(id)
  tagList(
    pickerInput(
      inputId = ns("sci"),
      label = "Scientific name", 
      choices = unique(data$scientificName),
      selected = unique(data$scientificName)[1] 
      
    ),
    actionButton(ns("action"),"Submit")
  )
  
}

sideServer <- function(id) {
  moduleServer(
    id,
    function(input, output, session) {
      
      # define a reactive and return it
      react<-eventReactive(input$action,{
        
        omited <-subset(data, data$scientificName %in% isolate(input$sci))
      })
      
      return(react)
      
    })
}
# In this case this server not needed but using uiOuput/renderUI in real case
# sideServer <- function(id) { moduleServer(id,function(input, output, session) { })}

# Define the UI and server functions for the map
mapUI <- function(id) {
  ns <- NS(id)
  tagList(
    leafletOutput(ns("map"))
  )
}

mapServer <- function(id, city) {
  moduleServer(
    id,
    function(input, output, session) {
      output$map<-renderLeaflet({
        
        leaflet(data = city()) %>% addTiles() %>%
          addMarkers(~decimalLatitude, ~decimalLongitude, popup = ~as.character(scientificName), label = ~as.character(scientificName))
      })
    })
}

# Build ui & server and then run
ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(sideUI("side")),
  dashboardBody(mapUI("mapUK"))
)
server <- function(input, output, session) {
  
  # use the reactive in another module
  city_input <- sideServer("side")
  mapServer("mapUK", city_input)
  
}
shinyApp(ui, server)

1. Always use tagList() inside UI in modules. Sometimes it will work without it, but usually not.
2. In this line: actionButton(ns("action"),"Submit") you have missed ns().
3. In this line: leaflet(data = city()) %>% addTiles() %>% you have used react() instead of city(). That's wrong, because you don't have parameter react in your function, but city, so you have to refer to city. This is the same as in normal function, i.e. you need to refer to the parameter in function to use arguments passed to this function.