conditionalPanel when 2 files are uploaded

Question

I am trying to display a panel in shiny only when both files are uploaded.

shinyApp(
  ui = fluidPage(
    fileInput('fileInput_pd', 'Add the file'),
    fileInput('fileInput_di', 'Add the file'),
    
    conditionalPanel(
      condition = "(input.fileInput_pd && input.fileInput_di) is true",
      selectInput("smoothMethod", "Method",
                  list("lm", "glm", "gam", "loess", "rlm"))
    ),
    
    downloadButton('report', 'Generate report')
  ),
  server = function(input, output) {
    
    observe({
      if(is.null(input$fileInput_pd) | is.null(input$fileInput_di)) {
        return()
      } else {
        var_example <- 2
      }
    }
    )
  }
)

With the code as above, it generates the conditionalPanel at the start. Any sugestions of what can I do?

Answer 1

Rather than trying to read in input directly, you can create a reactive variable on the output that indicates when the data is ready to be used. For example

library(shiny)
shinyApp(
  ui = fluidPage(
    fileInput('fileInput_pd', 'Add the file'),
    fileInput('fileInput_di', 'Add the file'),
    
    conditionalPanel(
      condition = "output.filesUploaded",
      selectInput("smoothMethod", "Method",
                  list("lm", "glm", "gam", "loess", "rlm"))
    ),
    
    downloadButton('report', 'Generate report')
  ),
  server = function(input, output) {
    
    observe({
      if(is.null(input$fileInput_pd) | is.null(input$fileInput_di)) {
        return()
      } else {
        var_example <- 2
      }
    }
    )
    output$filesUploaded <- reactive({
      val <- !(is.null(input$fileInput_pd) | is.null(input$fileInput_di))
      print(val)
    })
    outputOptions(output, 'filesUploaded', suspendWhenHidden=FALSE)
  }
)

This was basically just sightly adapted from this answer and changed to it checks two files instead of one,