Shiny: Server-side selectInput values

[Enuma]

Hi.

I am trying to add values to selectInput based on distinct values found in the dataframe. I found one way using uiOutput in the server function and renderUI on UI side. See example:

server <- function(input, output, session) {
  data("mtcars")
  output$select_cars = renderUI({
    selectInput("cyl",
                label = "Select cylinder",
                choices = mtcars %>% distinct(cyl) %>% pull %>% append("All", after = 0))
  })
}

ui = fluidPage(
  uiOutput("select_cars")
)

shinyApp(ui, server)

I am wondering whether a better option shouldn't be just plug output values to selectInput rendered on UI side (I do not have an example for this cause I am having trouble figuring it out). So the questions are: Is there an elegant way to do this as described? What are the best practices? Is there any speed difference between these two options?

Thank you!

[pieterjanvc]

Hi,

Shiny has an update function for every type of input. It's just the name of the UI element with a prefix of "update". So selectInput --> updateSelectInput.

See example:

library(shiny)
library(dplyr)

ui <- fluidPage(
  selectInput("myInput", "Choose:", choices = "")
)

server <- function(input, output, session) {
  data("mtcars")
  
  updateSelectInput(session, "myInput", 
                    choices =  mtcars %>% distinct(cyl) %>% 
                    pull %>% append("All", after = 0))
}

shinyApp(ui, server)

Hope this helps,
PJ

[Enuma]

Thanks, PJ. Works as intended.