shiny DT package dataTableOutput does not allow observe to monitor selected rows

Question

I have a shiny interface where I have two DT tables. I want the second table to render based on the output of a reactive expression (which works) combined with the selected data from the first table. However, when I write the observer for the second DT renderTable expression the entire observer does not react to changes in selected rows. I guess this is because the input$table_selected_rows is nowhere defined in the code but in some way inherent to the DT package (I only define input$table). The code for the second table is

row<-reactive({
    print("check")
    input$table_selected_rows
  })
  observe({
    a=row()
    print(a)
    if(length(a)>0){
      res=dtf()
      ID=res[a,]
      res=res[which(res$ID==ID),]
      output$table2=DT::renderDataTable(dplyr::distinct(res),
                                        selection=list(mode="single",target="row"))
      }

  })
  observe({
  row()
  })

In the code above "check" is only printed once at the initialization of the code and not when I select rows from the first table in my session. How do I force shiny to monitor input$table_selected_rows so that the second table is reactive to the first table?

Answer 1

The problem in your code is, that you switched the input name:

table_selected_rows should be table_rows_selected . Please see chapter 2.1.1 here .

Here is a simple reproducible example:

library(shiny)
library(DT)
library(datasets)

ui <- fluidPage(
  DTOutput("Tab1"),
  DTOutput("Tab2")
)

server <- function(input, output, session) {
  output$Tab1 <- renderDT({iris}, selection=list(mode = "single", target = "row"))
  row <- reactive({input$Tab1_rows_selected})
  output$Tab2 <- renderDT({data.frame(row())})
}

shinyApp(ui, server)