Dowload a file without using downloadButton (nor downloadHandler ?)

[Dominique Emmanuel]

Hi,

For some reasons, I would like a shiny application that allows the user to download a file but without using downloadButton.

In my application, the download should begins when an action on my_input is done :
## Somewhere in the server function
my_file <-  "c:/an_excel_file.xlsx" # a path to an Excel file
a_name <- "my_downloaded_file.xlsx" # name of the file when downloaded on the client side

observeEvent(input$my_input# my_input do not refers to a downloadButton
, {
## ???? Some code using my_file and a_name and causing the start of downloading in the client side
})


How can I fill the ## ???? part ?
With something like session$registerDownload ?

Best regards,
Dominique






 

[Dominique Emmanuel]

NB : my_file is a file path in the server side (maybe in the same directory than ui.R or server.R for instance)

[Dominique Emmanuel]

I have found a (not so pretty) solution (but it works), so I share it :

1. First, in the UI part I create an invisible download link (I set label ="" to get it invisible => it allows to declare a downloadLink but not to see it):
downloadLink("downloadData",label="")

2. I also declare (in the UI part) this javascript code (inspired by this) :
tags$head(tags$script(HTML('
                           Shiny.addCustomMessageHandler("jsCode",
                           function(message) {
                           eval(message.value);
                           });'
)))
3. In the server part I create thise observer (partially inspired by this)
observeEvent(input$my_own_trigger, {
  output$downloadData<<-downloadHandler(filename = x$Nom,content = function(file)file.copy(file0,file) )
  jsinject <- "setTimeout(function(){window.open($('#downloadData').attr('href'))}, 100);"
  session$sendCustomMessage(type = 'jsCode', list(value = jsinject))    
})

So now I can produce a download in the client side with any trigger (input$my_own_trigger)

[Danny Challis]

This worked quite well except that now Chrome is blocking the download as a pop-up. Policy doesn't allow adding exception. Did you find a way around this problem too?

Thanks!

Danny.

[Joe Cheng]

I don't know of a way around this; and if there was a workaround, I imagine the Chrome team would probably consider it a bug that needs to be fixed.

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