How to get choices values of SelectInput in Shiny? - shiny

Question

How can I get the list of choices in a SelectInpute?
ui.R
selectInput(inputId = "select_gender",
label = "Gender",
choices = c("Male","Female"),
width = 150
)
server.R
# Something like...
genders <- input$select_gender["choices"]
# So that the gender would be:
> genders
[1] Male Female

Answer 1

From the scoping rules of Shiny:
Objects defined in global.R are similar to those defined in app.R outside of the server function definition, with one important difference: they are also visible to the code in the ui object. This is because they are loaded into the global environment of the R session; all R code in a Shiny app is run in the global environment or a child of it.
However, this doesn't mean that objects defined in the app.R can't be used on both the UI and Server side, they just belong to a different environment.
For example:
library("shiny")
library("pryr")
# or in global.R
genders <- c("Male", "Female")
gen_env <- where("genders")
par_env <- parent.env(gen_env)
ui <- fluidPage(
selectInput("shiny_gender", "Select Gender", choices = genders),
verbatimTextOutput("selected_gender_index"),
p("The `genders` object belongs to the environment:"),
verbatimTextOutput("gen_env_print"),
p("Which is the child of the environment:"),
verbatimTextOutput("par_env_print")
)
server <- function(input, output) {
output$selected_gender_index <- renderPrint({
# use the 'genders' vector on the server side as well
which(genders %in% input$shiny_gender)
})
output$gen_env_print <- renderPrint(gen_env)
output$par_env_print <- renderPrint(par_env)
}
shinyApp(ui = ui, server = server)

Answer 2

I've looked for get choices of selectinput but without recompute the choices. For example if the datas come from database, or file or other source.
And I didn't get answer. (I get this question but not the solution for me).
Here is ma solution which also could set the selectinput from the server:
set the choices list in a reactive function
build the selectinput in the server side (with the choices list reactive function)
set and get the selectinput in the server side
Here is the code
options(encoding = "UTF-8")
library("shiny")
library("pryr")
ui <- fluidPage(
uiOutput("shiny_gender.UI"),
verbatimTextOutput("selected_gender_index"),
p("The `genders` object belongs to the environment:"),
verbatimTextOutput("gen_env_print"),
p("Which is the child of the environment:"),
verbatimTextOutput("par_env_print"),
p(""),
textInput("set_input_txt","Set the car in letter (for example `Datsun 710`)",
#" Set the Select Input Male / Female ",
""),
actionButton("submit","submit")
)
server <- function(input, output, session) {
observeEvent(
c(input$submit),
{
if (input$submit>0) {
updateSelectInput(session, "shiny_gender",
# server = TRUE, if updateSelectizeInput
choices =shiny_gender.list(),
selected = input$set_input_txt
)
}
}
)
shiny_gender.list <- reactive ({
#c("Male", "Female")
rownames(mtcars)
})
output$shiny_gender.UI <- renderUI({
selectInput( "shiny_gender",
label="Select car",#"Select Gender",
choices =shiny_gender.list()
)
})
output$selected_gender_index <- renderPrint({
which(shiny_gender.list() %in% input$shiny_gender)
})
output$gen_env_print <- renderPrint(where("shiny_gender.list"))
output$par_env_print <- renderPrint(parent.env( where("shiny_gender.list")))
}
shinyApp(ui = ui, server = server)