Cookies are name-value pairs that are saved in a user’s browser by a website. Cookies allow websites to persist information about the user and their use of the website. The goal of {cookies} it to make it as easy as possible to use cookies in shiny apps.
Install the released version of {cookies} from CRAN:
install.packages("cookies")Or install the development version of {cookies} from GitHub with:
# install.packages("remotes")
remotes::install_github("r4ds/cookies")Several potential use cases motivated the creation of this package.
In general, cookies can be used to save some sort of setting about the user. This allows you to restore their state (or otherwise know something about that user) the next time they load your app.
Here we’ll use a simple example to demonstrate this concept.
library(cookies)
library(shiny)
# Wrap your ui with add_cookie_handlers() to enable cookies.
ui <- add_cookie_handlers(
fluidPage(
titlePanel("A Simple App"),
fluidRow(
sliderInput(
"number_selector",
label = paste(
"Select a number.",
"This selector sets the cookie value.",
"It also initializes with the cookie value.",
"Refresh to see it remembered.",
sep = "\n"
),
min = 1,
max = 10,
value = 1
),
sliderInput(
"number_selector_no_cookie",
label = paste(
"Select a number.",
"This one is not connected to the cookie.",
"When you refresh, it will always initialize to 1.",
sep = "\n"
),
min = 1,
max = 10,
value = 1
)
)
)
)
server <- function(input, output, session) {
# When the value changes, set a cookie.
observeEvent(
input$number_selector,
{
set_cookie(
cookie_name = "selected_number",
cookie_value = input$number_selector
)
}
)
# Initialize the top slider from any cookies that come in at the start.
observeEvent(
get_cookie("selected_number"),
updateSliderInput(
inputId = "number_selector",
value = get_cookie("selected_number")
),
once = TRUE
)
}
shinyApp(
ui,
server,
# Cookies only work in an actual browser.
options = list(
launch.browser = TRUE
)
)If you run that code, make selections, and refresh your browser, you should see that the first slider is remembered, while the second is not.
Please note that the cookies project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.