Use functions or loops to create shiny UI elements - r

Question

I am creating a shiny app and realized I am repeating a particular UI element so I am wondering if there is a way to wrap this in a function and supply parameters to make it work in different cases. In my server file, I have
output$loss <- renderUI({
req(input$got)
if(input$got %in% Years) return(numericInput('got_snow', label = 'John Snow', value = NA))
if(!input$got %in% Years) return(fluidRow(column(3)))
})
and in the ui file, I have:
splitLayout(
cellWidths = c("30%","70%"),
selectInput('got', label = 'Select age', choices = c('',Years) , selected = NULL),
uiOutput("loss")
)
Since I find myself using these several times and only changing a few things in both the UI and server files, I wanted to wrap these in a function and use them as and when I please. I tried this for the server file
ui_renderer <- function(in_put, label, id){
renderUI({
req(input[[in_put]])
if(input[[in_put]] %in% Years) return(numericInput(id, label = label, value = NA))
if(!input[[in_put]] %in% Years) return(fluidRow(column(3)))
})
}
output$p_li <- ui_renderer(input='li', "Enter age", id="c_li")
and in my ui file, I put
uiOutput('c_li')
but it's not working. Any help is greatly appreciated.

Answer 1

I was unable to test your code since there was no minimal working example. I don't know if this is a typo in your example, but your are trying to render c_li, but your output is called p_li. Not sure how wrapping a render object in a standard function works, but I have done something similar using reactive values instead.
This is a minimal example using some of your terminology. It is not a working example, but an outline of the idea to my proposed solution.
# Set up the UI ----
ui <- fluidPage(
uiOutput("loss")
)
# Set up the server side ----
server <- function(input, output, session) {
# Let us define reactive values for the function inputs
func <- reactiveValues(
value <- "got",
label <- "select age",
id <- "xyz"
)
# Set up an observer for when any of the reactive values change
observeEvent({
func$value
func$label
func$id
}, {
# Render a new UI any time a reactive value changes
output[["loss"]] <- renderUI(
if (input[[func$value]] %in% years) {
numericInput(func$id, label = func$label, value = NA)
} else {
fluidRow(
column(3)
)
}
)
})
}
# Combine into an app ----
shinyApp(ui = ui, server = server)
The general idea is to define a set of reactive values and set up an observer that will render the UI every time one or more of the reactive values change. You can assign a new value to any of the reactive values using direct assignment, e.g. current$value <- "object_two". Making that change will update the UI using Shiny's reactive pattern, which means you only need to change one value to update the UI.