How to listen for more than one event expression within a Shiny observeEvent

Question

I want two different events to trigger an observer. It was suggested here that this should work. But it seems that it depends only on the second event.

observeEvent({    input$spec_button   mainplot.click$click }, { ... } ) 

Have a look at the example.

ui <- shinyUI(bootstrapPage(     actionButton("test1", "test1"),     actionButton("test2", "test2")) )  server <- shinyServer(function(input, output) {     observeEvent({         input$test1         input$test2     }, {         print('Hello World')     }) })  shinyApp(ui, server) 

Once you click button test1 nothing happens. If you click button test2 it prints to your console. Once test2 button was pressed clicking test1 prints the message. That is a strange behaviour.

Another suggestion in that link was to use

list(input$test1, input$test2) 

Which prints the message even without clicking the buttons.

Answer 1

This should do it, note that you still have to check if the buttons were clicked as mentioned by @MrFlick

1. You can use reactive expression

#rm(list = ls()) library(shiny) ui <- shinyUI(bootstrapPage(   actionButton("test1", "test1"),   actionButton("test2", "test2")) )  server <- shinyServer(function(input, output) {    toListen <- reactive({     list(input$test1,input$test2)   })   observeEvent(toListen(), {     if(input$test1==0 && input$test2==0){       return()     }     print('Hello World')   }) })  shinyApp(ui, server) 

2. As per example given by @MrFlick (now deleted)

#rm(list = ls()) library(shiny) ui <- shinyUI(bootstrapPage(   actionButton("test1", "test1"),   actionButton("test2", "test2")) )  server <- shinyServer(function(input, output) {    observeEvent(input$test1 | input$test2, {     if(input$test1==0 && input$test2==0){       return()     }     print('Hello World')   }) })  shinyApp(ui, server) 

Answer 2

observeEvent is a wrapper for complex observe cases. In this particular case of an action when one or other reactive value changes, one could use a simple observe. This works:

require(shiny)     ui <- basicPage(       actionButton("test1", "test1"),       actionButton("test2", "test2")     )          server <- function(input, output, session){            observe( {         input$test1         input$test2         if(input$test1==0 && input$test2==0){           return()         }         print('Hello World')         })     }          shinyApp(ui, server) 

There is a point in using observeEvent with options to eliminate the return() call:

ui <- basicPage(   actionButton("test1", "test1"),   actionButton("test2", "test2") )  server <- function(input, output, session){    observeEvent(input$test1 | input$test2, { print('Hello World') } , ignoreInit = TRUE) }  shinyApp(ui, server)