3 Basic reactivity

3.3.6 Exercises

Server 1

• input$greeting –> output$greeting
• Inside renderText, name –> input$name
• Fixed code:

server1 <- function(input, output, server) {
  output$greeting <- renderText(paste0("Hello ", input$name))
}

Server 2

• Make greeting a reactive: greeting <- reactive(paste0("Hello ", input$name))
• Since greeting is now a reactive, add parenthesis around it: output$greeting <- renderText(greeting())
• Fixed code:

server2 <- function(input, output, server) {
  greeting <- reactive(paste0("Hello ", input$name))
  output$greeting <- renderText(greeting())
}

Server 3

• Spelling error: output$greting –> output$greeting
• Missing renderText()
• Fixed code:

server3 <- function(input, output, server) {
  output$greeting <- renderText(paste0("Hello ", input$name))
}

2. Solution at Mastering Shiny Solutions 2021

3. When you use range() or var(), other readers won’t know if you are using a reactive or the built-in R function.

Not sure why code fails, but maybe reading the chapter on Tidy evaluation will help.