How to update a SelectizeInput depending on a textInput in Shiny

Question

I have create one app that contains a textInput and a selectizeInput. Depending on the user's input and if the input can be found in one dataset, you will see all the possibilities according to that textInput in the selectizeInput.

In this way, if the user introduces a word that it is not in the dataset, the selectizeInput can't display any choice.

Everything works fine, but I found one problem. If the user starts writing a correct word, the user gets a dropdown list... and then, if the input is removed... the dropdown list is still there (the choices from selectizeInput are still there).

Here the code:

library(shiny)
library(dplyr)
library(stringr)

ui <- fluidPage(
  textInput("my_input", "Introduce a word"),
  selectizeInput(inputId = "dropdown_list", label = "Choose the variable:", choices=character(0)),
  
)

server <- function(input, output, session) {
  
  my_list <- reactive({
    req(input$my_input)
    data <- as.data.frame(storms)
    
    res <- subset(data, (grepl(pattern = str_to_sentence(input$my_input), data$name))) %>% 
      dplyr::select(name)
    
    res <- as.factor(res$name)
    
    
    return(res)
  })
  
  # This is to generate the choices (gene list) depending on the user's input.
  observeEvent(input$my_input, {
    updateSelectizeInput(
      session = session,
      inputId = "dropdown_list",
      choices = my_list(), options=list(maxOptions = length(my_list())),
      server = TRUE
    )
  })

}

shinyApp(ui, server)

Do you know how can I remove the choices from the selectizeInput if the user deletes the input?

Thanks very much in advance

Regards

Answer 1

The issue is the req(input$myinput). Hence, if the user deletes the input my_list() does not get updated. Instead of req you could use an if to check whether the input is equal to an empty string:

my_list <- reactive({
    if (!input$my_input == "") {
      data <- as.data.frame(storms)
      
      res <- subset(data, grepl(pattern = str_to_sentence(input$my_input), data$name), name)
      
      res <- as.factor(res$name)
      
      return(res)
    } 
  })