R help - Oct 2013 - Trying it 'isolate' correctly in Shiny

Hello!

I am learning Shiny. In my ui am allowing the user to read in 3 files. Here
is a piece of my ui.r code:

  sidebarPanel(
    fileInput('file1','Select File 1:'),
    fileInput('file2','Select File 2:'),
    fileInput('fileopt','Select Optional File:'),
    actionButton("goButton","RUN")
  ),

Then I want my server code (below) to do something based on EITHER all 3
files that were read in OR - if the 3rd file was not uploaded - based on
just the first 2 files.
However, it's not working. Maybe what I am doing with myflag is wrong?
Or maybe I am isolating incorrectly at the very bottom?

Thank you so much for any pointers!
Dimitri

shinyServer(function(input,output){

  # Drop-down selection box for Input file 1:
  renderUI({
    fileInput('utils')
  })

  # Drop-down selection box for Input file 2:
  renderUI({
    fileInput('attrib')
  })

  # Drop-down selection box for Input file 3 (optional):
  renderUI({
    fileInput('test')
  })


  myflag=1

  bigone<-reactive({
    inFile1<-input$file1
    inFile2<-input$file2
    inFile3<-input$fileopt

    if (is.null(inFile3)) myflag=0

    forout1<-read.csv(inFile1$datapath)
    forout2<-read.csv(inFile2$datapath)

    if(myflag==1) forout3<-read.csv(inFile3$datapath)

    if(myflag==1){
      out1<-cbind(forout1,forout2,forout3)
      out2<-cbind(forout2,forout1,forout3)
    } else {
      out1<-cbind(forout1,forout2)
      out2<-cbind(forout2,forout1)

    }
    return(list(out1,out2))
  })

  # Summary statistics for the moments data frame (for testing purposes):

  output$myoutput1<-renderPrint({
    input$goButton
    # Isolating:
    isolate(bigone()$out1)
    # bigone()$out1
  })

  output$myoutput2<-renderPrint({
    input$goButton
    # Isolating:
    isolate(bigone()$out2)
  })

})

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