[toc]
8 User feedback
8.1 Validation
8.1.1 Validating input
library(shiny);ui <- fluidPage(
shinyFeedback::useShinyFeedback(),
numericInput("n", "n", value = 10),
textOutput("half")
)
server <- function(input, output, session) {
half <- reactive({
even <- input$n %% 2 == 0
shinyFeedback::feedbackWarning("n", !even, "Please select an even number")
input$n / 2
})
output$half <- renderText(half())
};shinyApp(ui,server)
8.1.2 Cancelling execution with req()
ui <- fluidPage(
selectInput("language", "Language", choices = c("", "English", "Maori")),
textInput("name", "Name"),
textOutput("greeting")
)
server <- function(input, output, session) {
greetings <- c(
English = "Hello",
Maori = "Kia ora"
)
output$greeting <- renderText({
req(input$language, input$name)
paste0(greetings[[input$language]], " ", input$name, "!")
})
}
}
8.1.3 req() and validation
library(shiny);ui <- fluidPage(
shinyFeedback::useShinyFeedback(),
textInput("dataset", "Dataset name"),
tableOutput("data")
)
server <- function(input, output, session) {
data <- reactive({
req(input$dataset)
exists <- exists(input$dataset, "package:datasets")
shinyFeedback::feedbackDanger("dataset", !exists, "Unknown dataset")
req(exists, cancelOutput = T)
get(input$dataset, "package:datasets")
})
output$data <- renderTable({
head(data())
})
};shinyApp(ui,server)
8.1.4 Validate output
ui <- fluidPage(
numericInput("x", "x", value = 0),
selectInput("trans", "transformation",
choices = c("square", "log", "square-root")
),
textOutput("out")
)
server <- function(input, output, session) {
output$out <- renderText({
if (input$x < 0 && input$trans %in% c("log", "square-root")) {
validate("x can not be negative for this transformation")
}
switch(input$trans,
square = input$x ^ 2,
"square-root" = sqrt(input$x),
log = log(input$x)
)
})
};shinyApp(ui,server)
8.2 Notifications
ui <- fluidPage(
actionButton("goodnight", "Good night")
)
server <- function(input, output, session) {
observeEvent(input$goodnight, {
showNotification("So long")
Sys.sleep(1)
showNotification("Farewell")
Sys.sleep(1)
showNotification("Auf Wiedersehen")
Sys.sleep(1)
showNotification("Adieu")
})
};shinyApp(ui,server)
