Observer demoThis demo writes the value of the slider to a log file. If you can, check the file contents after moving the slider to confirm it's been appended to. In this example, what's visible in the client isn't what's interesting. The server is writing to a log file each time the slider value changes. |
function(input, output, session) {
# Create a random name for the log file
logfilename <- tempfile('logfile', fileext = '.txt')
output$logfile <- renderText({
sprintf("Log file: %s", logfilename)
})
# This observer adds an entry to the log file every time
# input$n changes.
obs <- observe({
cat(input$n, '\n', file = logfilename, append = TRUE)
})
session$onSessionEnded(function() {
# When the client ends the session, clean up the log file
# for this session.
unlink(logfilename)
})
output$text <- renderText({
paste0("The value of input$n is: ", input$n)
})
}fluidPage(
titlePanel("Observer demo"),
mainPanel(
p("This demo writes the value of the slider to a log file. If you can, check the file contents after moving the slider to confirm it's been appended to."),
verbatimTextOutput('logfile'),
fluidRow(
column(4, wellPanel(
sliderInput("n", "N:",
min = 10, max = 1000, value = 200, step = 10)
)),
column(8,
verbatimTextOutput("text"),
br(),
br(),
p("In this example, what's visible in the client isn't",
"what's interesting. The server is writing to a log",
"file each time the slider value changes.")
)
)
)
)