Usage of ellipsis within a shiny module

Question

I wonder, if it is possible to use ellipsis (...) in a shiny server module. I think the problem is that i cannot call the reactive value (as it is usual done with parentheses - value() ) within the server module.

Trying to make the ellipsis reactive ...() did also not work out. Anyone an idea how to solve this issue?

Thanks in advance!

renderPlotsUI = function(id) {
  ns = NS(id)
  tagList(plotOutput(ns("plot")))
}

renderPlots = function(input, output, session, FUN, ...) {
  output$plot = renderPlot({FUN(...)})
}

# APP BEGINS
ui = fluidPage(
  renderPlotsUI("plot1")
) 
server = function(input, output, session) {
  callModule(renderPlots, "plot1", FUN=plot, x = reactive(mtcars))
}

shinyApp(ui, server)

Answer 1

You can convert the ellipsis to a list with list and then use lapply and do.call to call your function. I slightly changed your example to showcase how to pass inputs from the ui to the function.

library(shiny)

renderPlotsUI = function(id) {
  ns = NS(id)
  tagList(plotOutput(ns("plot")))
}

renderPlots = function(input, output, session, FUN, ...) {
  output$plot = renderPlot({
    args_evaluated <- lapply(list(...), function(x){x()})      
    do.call(FUN, args_evaluated)
  })
}

shinyApp(
  fluidPage(
    sliderInput("n", "n", 1, 10, 5),
    renderPlotsUI("plot1")
  ) , 
  function(input, output, session) {
    callModule(renderPlots, "plot1", FUN = plot, x = reactive({1:input$n}))
  }
)