Is it possible for multiple users of the same app to make changes to the same set of reactive values?
This question ( handling multiple users simulaneously in an R Shiny app ) suggests that multiple users in different sessions can make changes to the same value (by declaring it outside of server()
and using <<-
instead of <-
) But that is for just plain old values/variables. Is this possible for reactive values?
Ideally, I would like a change made by user A to be immediately reflected in some output viewed by user B.
Here's a minimal working example based on RStudio's default one-file Shiny app:
library(shiny)
slidervalue <- 30
# Define UI for application that draws a histogram
ui <- fluidPage(
# Application title
titlePanel("Old Faithful Geyser Data"),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
sliderInput("bins",
"Number of bins:",
min = 1,
max = 50,
value = slidervalue)
),
# Show a plot of the generated distribution
mainPanel(
plotOutput("distPlot"),
textOutput('txt')
)
)
)
# Define server logic required to draw a histogram
server <- function(input, output, session) {
observe({
slidervalue <<- input$bins
})
reactive_slidervalue <- reactivePoll(100, session,
checkFunc = function() { slidervalue },
valueFunc = function() { slidervalue }
)
output$txt <- renderText(reactive_slidervalue())
observe({
updateSliderInput(session, 'bins', value = reactive_slidervalue())
})
output$distPlot <- renderPlot({
# generate bins based on input$bins from ui.R
x <- faithful[, 2]
bins <- seq(min(x), max(x), length.out = reactive_slidervalue() + 1)
# draw the histogram with the specified number of bins
hist(x, breaks = bins, col = 'darkgray', border = 'white')
})
}
# Run the application
shinyApp(ui = ui, server = server)
Basically, I am using a global variable (as you and and the post suggested), and then hooked it back into server by using the reactivePoll
function to make the external dependency reactive.
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