Using date input via Dateinput to be filename - date

Question

I have a shiny UI which allows user to select a date via dateinput box. Given output from this will be backup daily hence would like to use such "date", eg 20181224 as part of filename.
library(shiny)
library(shinyFiles)
ui <- fluidPage(
sidebarPanel(
dateInput("COBInput", "Select a Date", value=Sys.Date())
))
server <- function(input,output,session){
COB <- reactive(as.Date(input$COBInput,format="%Y-%m-%d"))
COB2 <- paste(
"Test",as.character(
format(input$COBInput,format="%Y-%m-%d",'%Y')
)
)}
shinyApp(ui,server)
Error that I got :
Listening on http://127.0.0.1:4973
Warning: Error in .getReactiveEnvironment()$currentContext: Operation not allowed
without an active reactive context. (You tried to do something that can only be
done from inside a reactive expression or observer.)
54: stop
53: .getReactiveEnvironment()$currentContext
52: .subset2(x, "impl")$get
51: $.reactivevalues
47: server [N:/AdHoc Query/R/FFVA/DateInputTest/ShinyApp.R#42]
Error in .getReactiveEnvironment()$currentContext() :
Operation not allowed without an active reactive context. (You tried to do something that can only be done from inside a reactive expression or observer.)
I would expect for each day, I could save file with name like "Daily20181224","Daily20181221" etc

Answer 1

I was exactly not clear about the requirements but tried using textoutput which can give you idea about how to generate the filename.
library(shiny)
library(shinyFiles)
ui <- fluidPage(
sidebarPanel(
dateInput("COBInput", "Select a Date", value=Sys.Date()),
textOutput("filename")
))
server <- function(input,output,session){
output$filename<-renderText({
input_date<-input$COBInput
year <- as.numeric(format(input_date,'%Y'))
month<-as.numeric(format(input_date,'%m'))
day<-as.numeric(format(input_date,'%d'))
paste0("Daily",year,month,day)
})
}
shinyApp(ui,server)
I think you can generate the filenames now
One thing I like to say about ShinyFiles - I think you are aware that it can only be used for server side file browsing after deployment.