Shiny: How to print in log the name of updated object? - r

Question

I try to print in log an input which has been updated by a user in an app. Something very close can be done with observeEvent.
observeEvent(c(input$integer, input$decimal, input$range), {
flog.info(glue::glue('The user updated a value!'))
})
But I want to see in log the name of updated object without its containing values. How is it possible to do?
if (interactive()) {
library(shiny)
library(futile.logger)
library(glue)
ui <- fluidPage(
titlePanel("Sliders"),
sidebarLayout(
sidebarPanel(
sliderInput("integer", "Integer:",
min = 0, max = 1000,
value = 500),
sliderInput("decimal", "Decimal:",
min = 0, max = 1,
value = 0.5, step = 0.1),
sliderInput("range", "Range:",
min = 1, max = 1000,
value = c(200,500))
),
mainPanel(
tableOutput("values")
)
)
)
# Define server logic for slider examples ----
server <- function(input, output) {
observeEvent(c(input$integer, input$decimal, input$range), {
flog.info(glue::glue('The user updated a value!'))
})
# Reactive expression to create data frame of all input values ----
sliderValues <- reactive({
data.frame(
Name = c("Integer",
"Decimal",
"Range"),
Value = as.character(c(input$integer,
input$decimal,
paste(input$range, collapse = " "))),
stringsAsFactors = FALSE)
})
# Show the values in an HTML table ----
output$values <- renderTable({
sliderValues()
})
}
# Create Shiny app ----
shinyApp(ui, server)
}

Answer 1

A solution with the help of the shiny:inputchanged event:
library(shiny)
js <- "
$(document).on('shiny:inputchanged', function(e) {
if(e.name != 'updated' && e.name != '.clientdata_output_values_hidden'){
Shiny.setInputValue('updated', e.name, {priority: 'event'});
}
});"
ui <- fluidPage(
tags$head(tags$script(HTML(js))),
titlePanel("Sliders"),
sidebarLayout(
sidebarPanel(
sliderInput("integer", "Integer:",
min = 0, max = 1000, value = 500),
sliderInput("decimal", "Decimal:",
min = 0, max = 1, value = 0.5, step = 0.1),
sliderInput("range", "Range:",
min = 1, max = 1000, value = c(200,500))
),
mainPanel(
tableOutput("values")
)
)
)
server <- function(input, output) {
observeEvent(input$updated, {
# do something with the name of the updated input,
# e.g flog.info(glue::glue(input$updated))
print(input$updated)
})
sliderValues <- reactive({
data.frame(
Name = c("Integer",
"Decimal",
"Range"),
Value = as.character(c(input$integer,
input$decimal,
paste(input$range, collapse = " "))),
stringsAsFactors = FALSE)
})
output$values <- renderTable({
sliderValues()
})
}
shinyApp(ui, server)