'Reset inputs' button in shiny app

Question

I would like to implement a 'Reset inputs' button in my shiny app.

Here is an example with just two inputs where I'm using the update functions to set the values back to the default values:

library(shiny)  runApp(list(    ui = pageWithSidebar(      headerPanel("'Reset inputs' button example"),      sidebarPanel(       numericInput("mynumber", "Enter a number", 20),       textInput("mytext", "Enter a text", "test"),       tags$hr(),       actionButton("reset_input", "Reset inputs")     ),      mainPanel(       h4("Summary"),       verbatimTextOutput("summary")     )    ),    server = function(input, output, session) {      output$summary <- renderText({       return(paste(input$mytext, input$mynumber))     })      observe({       input$reset_input       updateNumericInput(session, "mynumber", value = 20)       updateTextInput(session, "mytext", value = "test")     })   }  )) 

What I would like to know is if there is also a function that sets back everything to default? That would be useful in case of multiple inputs.

Additionally, I'm not sure if my use of the observe function in order to detect when the action button was hit is the 'proper way' of handling the action buttons?

Answer 1

There isn't such a function in shiny, however, here's a way to accomplish this without having to essentially define your inputs twice. The trick is to use uiOutput and wrap the inputs you want to reset in a div whose id changes to something new each time the reset button is pressed.

library(shiny)  runApp(list(    ui = pageWithSidebar(      headerPanel("'Reset inputs' button example"),      sidebarPanel(       uiOutput('resetable_input'),       tags$hr(),       actionButton("reset_input", "Reset inputs")     ),      mainPanel(       h4("Summary"),       verbatimTextOutput("summary")     )    ),    server = function(input, output, session) {      output$summary <- renderText({       return(paste(input$mytext, input$mynumber))     })      output$resetable_input <- renderUI({         times <- input$reset_input         div(id=letters[(times %% length(letters)) + 1],             numericInput("mynumber", "Enter a number", 20),             textInput("mytext", "Enter a text", "test"))     })    } )) 

Answer 2

First of all, your use of the observer is correct, but there is another way that's slightly nicer. Instead of

observe({   input$reset_input   updateNumericInput(session, "mynumber", value = 20)   updateTextInput(session, "mytext", value = "test") }) 

You can change it to

observeEvent(input$reset_input, {   updateNumericInput(session, "mynumber", value = 20)   updateTextInput(session, "mytext", value = "test") }) 

Also note that you don't need to explicitly "return" from a renderText function, the last statement will automatically be used.

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Regarding the main question: Matthew's solution is great, but there's also a way to achieve what you want without having to move all your UI into the server. I think it's better practice to keep your UI in the UI file just because separation of structure and logic is generally a good idea.

Full disclaimer: my solution involves using a package that I wrote. My package shinyjs has a reset function that allows you to reset an input or an HTML section back to its original value. Here is how to tweak your original code to your desired behaviour in a way that will scale to any number of inputs without having to add any code. All I had to do is add a call to useShinyjs() in the UI, add an "id" attribute to the form, and call reset(id) on the form.

library(shiny)  runApp(list(    ui = pageWithSidebar(      headerPanel("'Reset inputs' button example"),      sidebarPanel(       shinyjs::useShinyjs(),       id = "side-panel",       numericInput("mynumber", "Enter a number", 20),       textInput("mytext", "Enter a text", "test"),       tags$hr(),       actionButton("reset_input", "Reset inputs")     ),      mainPanel(       h4("Summary"),       verbatimTextOutput("summary")     )    ),    server = function(input, output, session) {      output$summary <- renderText({       return(paste(input$mytext, input$mynumber))     })      observeEvent(input$reset_input, {       shinyjs::reset("side-panel")     })   }  ))