modularise a currently working dropdown "updateSelectInput" shiny input

I have some data which looks like:

# A tibble: 100 × 5
   purchase_price provincia     municipio                                   distrito         zona                              
            <dbl> <chr>         <chr>                                       <chr>            <chr>                             
 1         207000 Gipuzkoa      Bajo Bidasoa                                Irun             Pinar - Anaka - Belaskoenea       
 2          65000 Valencia      Valencia, Zona de                           Valencia Capital Els Orriols                       
 3          62000 Valencia      Valencia, Zona de                           Valencia Capital Barrio de Benicalap               
 4         200000 Valencia      Valencia, Zona de                           Valencia Capital Barrio de Benimaclet              
 5         293000 Málaga        Costa del Sol Occidental - Zona de Estepona Estepona         Parque Central                    
 6          80000 Araba - Álava Laguardia - Rioja Alavesa                   Navaridas        NA                                
 7          96500 Tarragona     Tarragonès                                  Salou            Mar i Camp - Platja dels Capellans
 8         119500 Jaén          Campiña de Jaén                             Marmolejo        NA                                
 9         149999 Tarragona     Tarragonès                                  Salou            Platja de Llevant                 
10         144000 Barcelona     Maresme                                     Mataró           Cerdanyola Sud

I am trying to modularise my code to make it more complete and clean.

For example I am trying to do something where I only define the UI and observeEvent once. My current solution I have to define it 3 times and I am trying to clean the code and be more "efficient".

ui_dygraph <- function(id) {
  ns <- NS(id)

  choices <- map_chr()
  
  tagList(
    tags$div(
      class = "panel-header",
      selectInput(
        ns("loc"), "Select dropdown",
        choices,
        width = NULL,
        selectize = TRUE,
        selected = choices[[1]]
      )
    )
  )
}

server_dygraph <- function(id){
  moduleServer(id, function(input, output, session){
    observeEvent()
  }
  )
}

Shiny App:

library(shiny)
library(tidyverse)
library(bslib)

# data <- ...

ui <-  fluidPage(
  fluidPage(
    theme = bs_theme(bootswatch = "minty"),
    title = "hi",
    fluidRow(
      column(2,
             selectInput("provinceSelect", label = "Select Province Data", choices = c()),
             selectInput("municipioSelect", label = "Select Municipio Variable", choices = c()),
             selectInput("distritoSelect", label = "Select Distrito Variable", choices = c())
      )
    ),
    tableOutput('filteredDataOUT')

  )
)



server <- function(input, output, session) {

  #####################################################################################
  ################################# Property Search ###################################
  #####################################################################################

  ## (1) ## first drop down - observe the selection
  observeEvent(input$provinceSelect,{
    updateSelectInput(
      session,
      "municipioSelect",
      choices = data %>% filter(provincia == input$provinceSelect) %>% select(municipio) %>% unique() %>% pull(municipio)
    )
  })
  # then update the second dropdown selections
  observe({
    updateSelectInput(
      session,
      "provinceSelect",
      choices = data %>% select(provincia) %>% unique() %>% pull(provincia)
    )
  })
  ## (1) ## Do the same for the second dropdown
  observeEvent(input$municipioSelect,{
    updateSelectInput(
      session,
      "distritoSelect",
      choices = data %>% filter(municipio == input$municipioSelect) %>% select(distrito) %>% unique() %>% pull(distrito)
    )
  })
  observe({
    updateSelectInput(
      session,
      "distritoSelect",
      choices = data %>% select(municipio) %>% unique() %>% pull(municipio))
  })

  #### new code

  filteredDATA = reactive(
    filteredData <- data %>%
      filter(provincia == input$provinceSelect & municipio == input$municipioSelect & distrito == input$distritoSelect) %>%
      select(-c("provincia", "municipio", "distrito"))
  )
  output$filteredDataOUT <- renderTable(
    filteredDATA()
  )
}

shinyApp(ui = ui, server = server)

Data:

data = structure(list(purchase_price = c(207000, 65000, 62000, 2e+05, 
293000, 80000, 96500, 119500, 149999, 144000, 298000, 135000, 
310000, 285000, 269000, 120000, 595000, 355000, 96000, 490000, 
195000, 235000, 197000, 70000, 215000, 169000, 124900, 195000, 
185000, 190000, 390348, 113500, 295000, 299995, 156000, 195000, 
185000, 260000, 370000, 180000, 105000, 249000, 390000, 295000, 
86999, 219900, 264999, 56800, 179900, 150000, 145000, 168500, 
160000, 180000, 168000, 42300, 119000, 350000, 390000, 110000, 
420000, 154000, 429000, 85000, 259000, 495000, 170000, 102490, 
469000, 245000, 138000, 127000, 1390000, 320000, 420000, 292000, 
87500, 120000, 475000, 170000, 61000, 255000, 49000, 226000, 
220000, 3e+05, 30000, 265000, 330000, 220000, 220000, 139000, 
880000, 75000, 220000, 76400, 150000, 46000, 25000, 170000), 
provincia = c("Gipuzkoa", "Valencia", "Valencia", "Valencia", 
"Málaga", "Araba - Álava", "Tarragona", "Jaén", "Tarragona", 
"Barcelona", "Barcelona", "Alicante", "Granada", "Málaga", 
"Barcelona", "Tarragona", "Tarragona", "Barcelona", "Valencia", 
"Tarragona", "Castellón", "Segovia", "Alicante", "Tarragona", 
"Málaga", "Girona", "Cantabria", "Barcelona", "Barcelona", 
"Barcelona", "Barcelona", "Sevilla", "Granada", "Barcelona", 
"Barcelona", "Cáceres", "Barcelona", "Valencia", "Gipuzkoa", 
"Santa Cruz de Tenerife", "Tarragona", "Almería", "Alicante", 
"Granada", "Tarragona", "Toledo", "Tarragona", "Huelva", 
"Castellón", "Albacete", "Madrid", "Girona", "Castellón", 
"Zaragoza", "Madrid", "Alicante", "Barcelona", "Barcelona", 
"Sevilla", "Castellón", "Valencia", "Málaga", "Alicante", 
"Lleida", "Girona", "Madrid", "Alicante", "Pontevedra", "Barcelona", 
"Illes Balears", "Málaga", "A Coruña", "Barcelona", "Barcelona", 
"Barcelona", "Málaga", "Cádiz", "Valencia", "Barcelona", 
"Toledo", "Castellón", "Barcelona", "Huelva", "Barcelona", 
"Tarragona", "A Coruña", "Ciudad Real", "Illes Balears", 
"Ourense", "Barcelona", "Barcelona", "Málaga", "Málaga", 
"Córdoba", "Tarragona", "Castellón", "Valencia", "Castellón", 
"Navarra", "Cádiz"), municipio = c("Bajo Bidasoa", "Valencia, Zona de", 
"Valencia, Zona de", "Valencia, Zona de", "Costa del Sol Occidental - Zona de Estepona", 
"Laguardia - Rioja Alavesa", "Tarragonès", "Campiña de Jaén", 
"Tarragonès", "Maresme", "Maresme", "Marina Baixa", "Vega de Granada", 
"Costa del Sol Occidental - Zona de Estepona", "Maresme", 
"Tarragonès", "Tarragonès", "Barcelonès", "Horta Nord", 
"Tarragonès", "Plana Baixa", "Cuéllar, Zona de", "Alacantí", 
"Baix Camp", "Costa del Sol Occidental - Zona de Benalmádena", 
"La Selva", "Costa Oriental", "Vallès Oriental", "Vallès Oriental", 
"Vallès Oriental", "Maresme", "Sierra Norte", "Vega de Granada", 
"Vallès Occidental", "Baix Llobregat Sud", "Llanos de Cáceres", 
"Barcelonès", "La Safor", "Donostialdea - Oarsoldea", "Tenerife", 
"Tarragonès", "Almería capital y entorno", "Alacantí", 
"Vega de Granada", "Tarragonès", "Los Montes de Toledo", 
"Tarragonès", "Huelva capital y entorno", "Plana Alta", 
"Sierra de Alcaraz - Campo de Montiel", "Zona Sur de Madrid", 
"La Selva", "Plana Alta", "Zaragoza, Zona de", "Madrid, Zona de", 
"Vega Baja", "Barcelonès", "Bages", "Sevilla capital y entorno", 
"Plana Alta", "Valencia, Zona de", "Costa del Sol Occidental - Zona de Estepona", 
"Marina Alta", "Segrià", "Alt Empordà", "Madrid, Zona de", 
"Marina Baixa", "Comarca de Vigo", "Vallès Occidental", 
"Mallorca", "Costa del Sol Occidental - Zona de Estepona", 
"Comarca de Ferrol", "Vallès Occidental", "Osona", "Osona", 
"Costa del Sol Occidental - Zona de Estepona", "La Janda", 
"Ribera Alta (Valencia)", "Osona", "Toledo, Zona de", "Plana Alta", 
"Osona", "Huelva capital y entorno", "Vallès Oriental", 
"Baix Penedès", "Comarca de Ferrol", "Alcudia (Ciudad Real)", 
"Mallorca", "Comarca de Ourense", "Vallès Occidental", "Vallès Occidental", 
"Costa del Sol Occidental - Zona de Estepona", "Málaga capital y entorno", 
"La Subbética", "Baix Penedès", "Plana Alta", "Valencia, Zona de", 
"Plana Baixa", "Comarca de Pamplona", "Campiña de Jerez"
), distrito = c("Irun", "Valencia Capital", "Valencia Capital", 
"Valencia Capital", "Estepona", "Navaridas", "Salou", "Marmolejo", 
"Salou", "Mataró", "Dosrius", "Benidorm", "Granada Capital", 
"Manilva", "Dosrius", "Roda de Berà", "Roda de Berà", "Barcelona Capital", 
"Puig", "Tarragona Capital", "Vila-real", "Marugán", "San Vicente del Raspeig / Sant Vicent del Raspeig", 
"Mont-roig del Camp", "Benalmádena", "Anglès", "Laredo", 
"Granollers", "Granollers", "Granollers", "Cabrils", "El Ronquillo", 
"Cenes de la Vega", "Santa Perpètua de Mogoda", "Sant Boi de Llobregat", 
"Cáceres Capital", "Barcelona Capital", "Barx", "Donostia - San Sebastián", 
"Tacoronte", "Salou", "Almería Capital", "El Campello", 
"Albolote", "Salou", "Nambroca", "Salou", "Huelva Capital", 
"Castellón de la Plana / Castelló de la Plana", "Alcaraz", 
"Fuenlabrada", "Riells i Viabrea", "Castellón de la Plana / Castelló de la Plana", 
"Zaragoza Capital", "Madrid Capital", "Torrevieja", "Badalona", 
"Castellgalí", "Sevilla Capital", "Cabanes", "Valencia Capital", 
"Estepona", "Dénia", "Lleida Capital", "Roses", "Madrid Capital", 
"L'Alfàs del Pi", "Vigo", "Sabadell", "Palma de Mallorca", 
"Estepona", "Fene", "Cerdanyola del Vallès", "Vic", "Vic", 
"Estepona", "Vejer de la Frontera", "Senyera", "Vic", "Toledo Capital", 
"Borriol", "Santa Eugènia de Berga", "Huelva Capital", "Sant Celoni", 
"Calafell", "Fene", "Almadén", "Palma de Mallorca", "Ourense Capital", 
"Terrassa", "Terrassa", "Estepona", "Málaga Capital", "Lucena", 
"Calafell", "Castellón de la Plana / Castelló de la Plana", 
"Valencia Capital", "Onda", "Pamplona / Iruña", "Jerez de la Frontera"
), zona = c("Pinar - Anaka - Belaskoenea", "Els Orriols", 
"Barrio de Benicalap", "Barrio de Benimaclet", "Parque Central", 
NA, "Mar i Camp - Platja dels Capellans", NA, "Platja de Llevant", 
"Cerdanyola Sud", "Can Massuet del Far", "Levante Alto", 
"Centro - Sagrario", "Manilva Pueblo", "Canyamars", NA, NA, 
"Vilapicina i la Torre Llobeta", "El Puig", "Llevant", "Centro", 
NA, "Centro", "Poble", "Zona Centro Comercial Torrequebrada", 
NA, "Zona Playa", "Lledoner", "Lledoner", "Lledoner", NA, 
NA, NA, NA, "Casablanca", "Mejostilla", "El Poble Sec - Parc de Montjuïc", 
NA, "Amara Zaharra - Arbaizenea", "Campo de Golf - Agua García - Juan Fernández", 
"Platja de Llevant", "Plaza de Toros - Santa Rita", "Playa Muchavista", 
NA, "Mar i Camp - Platja dels Capellans", NA, "Centre", "Tres Ventanas", 
"El Grao", NA, "El Naranjo", NA, "Oeste", "La Magdalena", 
"Recoletos", "Zona Carrefour - Urbanizaciones", "Sant Roc", 
NA, "Encarnación - Regina", NA, "Penya - Roja - Avda. Francia", 
"Bel - Air", "El Montgó", "Mariola", "Centre", "Embajadores - Lavapiés", 
"Escandinavia - Cautivador", "Casablanca - Calvario", "Creu Alta", 
"Son Serra - Sa Vileta", "Cancelada", NA, "Bellaterra", "El Sucre - El Nadal", 
"El Sucre - El Nadal", "Paraiso - Barronal", "Vejer", NA, 
"El Sucre - El Nadal", "Santa Bárbara", NA, NA, "La Orden", 
NA, "Segur Platja", NA, NA, "Cala Major", "Centro", "Barri del Centre", 
"Ca n'Aurell", "Cancelada", "Pinares de San Antón", NA, 
"Segur Platja", "Norte", "Beteró", NA, "San Juan", "El Rocío - La Milagrosa"
)), row.names = c(NA, -100L), class = c("tbl_df", "tbl", 
"data.frame"))

EDIT:

My attempt which doesn't work:

myProvLists = data %>%
pull(provincia) %>%
unique()
# UI component for the module
ui_location_selections <- function(id) {
ns <- NS(id)
selectInput("provinceSelect", label = "Select Province Data", choices = c(myProvLists))
selectInput("municipioSelect", label = "Select Municipio Variable", choices = c())
# selectInput("distritoSelect", label = "Select Distrito Variable", choices = c())
}
# Server component for the module
server_location_selections <- function(id){
moduleServer(id, function(input, output, session){
observeEvent(input$provinceSelect,{
updateSelectInput(
session,
"municipioSelect",
choices = data %>% filter(provincia == input$provinceSelect) %>% select(municipio) %>% unique() %>% pull(municipio)
)
})
## (1) ## first drop down - observe the selection
observeEvent(input$provinceSelect,{
updateSelectInput(
session,
"municipioSelect",
choices = data %>% filter(provincia == input$provinceSelect) %>% select(municipio) %>% unique() %>% pull(municipio)
)
})
}
)
}
# Call the module in the app
ui <- fluidPage(
ui_location_selections("provincias"),
ui_location_selections("municipios"),
renderUI(output$provincias)
)
server <- function(input, output, session, data) {
server_location_selections("provincias")
}
shinyApp(ui, server)

The solution below is not so much modularisation, but rather a restructuring of the update logic which only requires 2 observeEvents and the reactive renderTable for output.

The key points are

• defining the provincia choices directly in ui since they never have to be updated (which you also did in your own attempt)
• observeEvents triggered by the provincia and municipio dropdowns, which subsequently filter the full dataframe based on the choice and update the remaining choices for the next level dropdown menu
• no need for an observeEvent for the last dropdown in the hierarchy, because the reactiveTable updates based on this selection anyway

Out of habit, I replaced filteredDATA with a reactiveValues list values to carry intermediate datasets between reactive environments. This could instead always filter directly from data, so not strictly necessary.

library(shiny)
library(tidyverse)
library(bslib)

# data <- ...

ui <-  fluidPage(
  fluidPage(
    theme = bs_theme(bootswatch = "minty"),
    title = "hi",
    fluidRow(
      column(2,
             selectInput("provinceSelect", label = "Select Province Data", choices = data %>% pull(provincia) %>% unique()),
             selectInput("municipioSelect", label = "Select Municipio Variable", choices = c()),
             selectInput("distritoSelect", label = "Select Distrito Variable", choices = c())
      )
    ),
    tableOutput('filteredDataOUT')
    
  )
)


server <- function(input, output, session) {
  
  #reactive value list to update and access data in reactive environments
  values <- reactiveValues()
   
  ## filter dataset based on provinceSelect, and update municipioSelect with remaining choices
  observeEvent(input$provinceSelect,{
    values[['provincia_df']] <- data %>% filter(provincia == input$provinceSelect)
    updateSelectInput(
      session, "municipioSelect",
      choices = values[['provincia_df']] %>% pull(municipio) %>% unique()
    )
  })
  
  ## filter dataset also on municipioSelect, and update distritoSelect with remaining choices
  observeEvent(input$municipioSelect,{
    values[['municipio_df']] <- values[['provincia_df']] %>% filter(municipio == input$municipioSelect)
    updateSelectInput(
      session, "distritoSelect",
      choices = values[['municipio_df']] %>% pull(distrito) %>% unique()
    )
  })
  
  # final output is automaticall triggered by input$distritoSelect
  output$filteredDataOUT <- renderTable(
    values[['municipio_df']] %>% filter(distrito == input$distritoSelect) %>%
      select(-all_of(c("provincia", "municipio", "distrito")))
  )
}

shinyApp(ui = ui, server = server)