R Shiny - Dynamic download link in datatable - r

Question

I want to add a download link in each row of a datatable in shiny.
So far I have
server <- function(input, output) {
v<-eventReactive(input$button,{
temp<-data.frame(TBL.name=paste("Data ",1:10))
temp<-cbind(
temp,
#Dynamically create the download and action links
Attachments=sapply(seq(nrow(temp)),function(i){as.character(downloadLink(paste0("downloadData_",i),label = "Download Attachments"))})
)
})
# Table of selected dataset ----
output$table <- renderDataTable({
v()
}, escape = F)}
ui <- fluidPage(
sidebarPanel(
actionButton("button", "eventReactive")
),
mainPanel(
dataTableOutput("table")
)
)
I have the download links in the table for each row. Now I want to add a different file location for each row. For example, each download link will result in a download of a different zip-folder. Can I use downloadHandler for this?

Answer 1

I do not believe you can embed downloadButtons/downloadLinks directly in a datatable. However, you can create hidden downloadLinks that get triggered by links embedded in your table. This produces the same end result. To do so you must:
Dynamically generate downloadLinks/downloadButtons.
Use css to set their visibility to hidden.
Embed normal links/buttons in the table
Set the onClick field of these links to trigger the corresponding hidden downloadLink.
Here is code from an example using the mtcars dataset.
library(tidyverse)
library(shiny)
ui <- fluidPage(
tags$head(
tags$style(HTML("
.hiddenLink {
visibility: hidden;
}
"))
),
dataTableOutput("cars_table"),
uiOutput("hidden_downloads")
)
server <- function(input, output, session) {
data <- mtcars
lapply(1:nrow(data), function(i) {
output[[paste0("downloadData", i)]] <- downloadHandler(
filename = function() {
paste("data-", i, ".csv", sep="")
},
content = function(file) {
write.csv(data, file)
}
)
})
output$hidden_downloads <- renderUI(
lapply(1:nrow(data), function(i) {
downloadLink(paste0("downloadData", i), "download", class = "hiddenLink")
}
)
)
output$cars_table <- renderDataTable({
data %>%
mutate(link = lapply(1:n(),
function(i)
paste0('<a href="#" onClick=document.getElementById("downloadData',i, '").click() >Download</a>')
))
}, escape = F)
}
shinyApp(ui, server)

Answer 2

Since each downloadLink label must correspond to a name in output, I don't think there is a way to create an arbitrary set of downloads using the standard Shiny download* functions.
I solved this using DT and javascript. DT allows javascript to be associated with a datatable. The javascript can then tell Shiny to send a file to the client and the client can force the data to be downloaded.
I created a minimal example gist. Run in RStudio with:
runGist('b77ec1dc0031f2838f9dae08436efd35')

Answer 3

Safari is not supporting .click() anymore since v12.0. Hence, I adapted the hidden link solution from abanker with the dataTable/actionButton described by P Bucher, and the .click() workaround described here. Here is the final code:
library(shiny)
library(shinyjs)
library(DT)
# Random dataset
pName <- paste0("File", c(1:20))
shinyApp(
ui <- fluidPage( useShinyjs(),
DT::dataTableOutput("data"),
uiOutput("hidden_downloads") ),
server <- function(input, output) {
# Two clicks are necessary to make the download button to work
# Workaround: duplicating the first click
# 'fClicks' will track whether click is the first one
fClicks <- reactiveValues()
for(i in seq_len(length(pName)))
fClicks[[paste0("firstClick_",i)]] <- F
# Creating hidden Links
output$hidden_downloads <- renderUI(
lapply(seq_len(length(pName)), function(i) downloadLink(paste0("dButton_",i), label="")))
# Creating Download handlers (one for each button)
lapply(seq_len(length(pName)), function(i) {
output[[paste0("dButton_",i)]] <- downloadHandler(
filename = function() paste0("file_", i, ".csv"),
content = function(file) write.csv(c(1,2), file))
})
# Function to generate the Action buttons (or actionLink)
makeButtons <- function(len) {
inputs <- character(len)
for (i in seq_len(len)) inputs[i] <- as.character(
actionButton(inputId = paste0("aButton_", i),
label = "Download",
onclick = 'Shiny.onInputChange(\"selected_button\", this.id, {priority: \"event\"})'))
inputs
}
# Creating table with Action buttons
df <- reactiveValues(data=data.frame(Name=pName,
Actions=makeButtons(length(pName)),
row.names=seq_len(length(pName))))
output$data <- DT::renderDataTable(df$data, server=F, escape=F, selection='none')
# Triggered by the action button
observeEvent(input$selected_button, {
i <- as.numeric(strsplit(input$selected_button, "_")[[1]][2])
shinyjs::runjs(paste0("document.getElementById('aButton_",i,"').addEventListener('click',function(){",
"setTimeout(function(){document.getElementById('dButton_",i,"').click();},0)});"))
# Duplicating the first click
if(!fClicks[[paste0("firstClick_",i)]])
{
click(paste0('aButton_', i))
fClicks[[paste0("firstClick_",i)]] <- T
}
})
}
)