General input for different modules in shiny - r

Question

I have a ui and a server module in shiny just like in an example in 'Mastering Shiny' by Hadley Wickham:
histogramUI <-
function(id){
tagList(
selectInput(NS(id, "var"), "Variable", choices = names(mtcars)),
numericInput(NS(id, "bins"), "bins", value = 10, min = 1),
plotOutput(NS(id, "hist"))
)
}
histogramServer <-
function(id){
moduleServer(id, function(input, output, session){
data <- reactive(mtcars[[input$var]])
output$hist <- renderPlot({
hist(data(), breaks = input$bins, main = input$var)
}, res = 96)
})
}
Now I want to create the app with two inputs and outputs named by "hist1" and "hist2".
That works fine with the following code:
histogrammApp <-
function(){
ui <- fluidPage(
histogramUI("hist1"),
histogramUI("hist2")
)
server <- function(input, output, session){
histogramServer("hist1")
histogramServer("hist2")
}
shinyApp(ui, server)
}
Each plot has its own input parameters.
Let's say I want to have a general input bins instead so that both plots will have the same amount of breaks in a numericInput. How could I achieve this?
My first attempt was to remove the line numericInput(NS(id, "bins"), "bins", value = 10, min = 1), and place the line tagList(numericInput("bins", "bins", value = 10, min = 1)), before the line histogramUI("hist1"), but this did not work. I get the following error: Invalid breakpoints produced by 'breaks(x)': NULL. input$bins is NULL, I guess. I think because it is in a different namespace? How could I come up with the problem?

Answer 1

You should consider passing the input$bins as a reactive to histogramServer("hist1",reactive(input$bins)). Try this
histogramUI <- function(id){
tagList(
selectInput(NS(id, "var"), "Variable", choices = names(mtcars)),
#numericInput(NS(id, "bins"), "bins", value = 10, min = 1),
plotOutput(NS(id, "hist"))
)
}
histogramServer <- function(id,bins){
moduleServer(id, function(input, output, session){
data <- reactive(mtcars[[input$var]])
output$hist <- renderPlot({
hist(data(), breaks = bins(), main = input$var)
}, res = 96)
})
}
#histogrammApp <- function(){
ui <- fluidPage(
numericInput("bins", "Bins", value = 10, min = 1),
histogramUI("hist1"),
histogramUI("hist2")
)
server <- function(input, output, session){
histogramServer("hist1",reactive(input$bins))
histogramServer("hist2",reactive(input$bins))
}
shinyApp(ui, server)
# }
#
# histogrammApp()