Update checkboxGroupInput() choices after file upload - r

Question

I have a simple shiny app below. In this app I want the user to be able to upload his own csv and then automatically this will be added as a choice in the checkbox group below the other dataset "D.B" (which I create in my original app).
#ui.r
ui <- fluidPage(
# App title ----
titlePanel("Uploading Files"),
# Sidebar layout with input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# Input: Select a file ----
fileInput("file1", "Choose CSV File",
multiple = FALSE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",
".csv")),
uiOutput("checkbox"),
textInput("filename","Set Filename")
),
# Main panel for displaying outputs ----
mainPanel(
# Output: Data file ----
tableOutput("contents")
)
)
)
#server.r
server <- function(input, output) {
output$contents <- renderTable({
req(input$file1)
df <- read.csv(input$file1$datapath)
})
D.B <- reactive({
#some code that creates the dataset D.B.
})
output$checkbox<-renderUI({
checkboxGroupInput("datasetSelector","Specify the datasets to compare:", choices = c("D.B")
)
})
}

Answer 1

You could use a reactive value to store choices then add a choice everytime a file is uploaded. Use an observer to watch for file uploads (I also used the library rlist which gives me the append method).
library(rlist)
#ui.r
ui <- fluidPage(
# App title ----
titlePanel("Uploading Files"),
# Sidebar layout with input and output definitions ----
sidebarLayout(
# Sidebar panel for inputs ----
sidebarPanel(
# Input: Select a file ----
fileInput("file1", "Choose CSV File",
multiple = FALSE,
accept = c("text/csv",
"text/comma-separated-values,text/plain",
".csv")),
uiOutput("checkbox"),
textInput("filename","Set Filename")
),
# Main panel for displaying outputs ----
mainPanel(
# Output: Data file ----
tableOutput("contents")
)
)
)
#server.r
#fileOptions = list("D.B.")
server <- function(input, output, session) {
output$contents <- renderTable({
req(input$file1)
df <- read.csv(input$file1$datapath)
head(df)
})
fileOptions <- reactiveValues(currentOptions=c("D.B."))
observeEvent(input$file1, {
fileOptions$currentOptions = list.append(fileOptions$currentOptions, input$file1$datapath)
})
D.B <- reactive({
#some code that creates the dataset D.B.
})
output$checkbox<-renderUI({
checkboxGroupInput("datasetSelector","Specify the datasets to compare:", choices = fileOptions$currentOptions
)
})
}