3.2 A deeper dive into the server function

server <- function(input, output, session)

1. input
   

• list-like object
  
• used for receiving input (sent from the browser)
  
• read-only (no x <- ‘12’ in server; otherwise you’ll get an error)
  
• must be read in a reactive context (e.g. renderText() or reactive())
  • Otherwise, you’ll get an error.

2. output
   

• list-like object
  
• used for sending output
  
• ALWAYS use with a render fn() - sets up the reactive context & renders the HTML.

ui <- fluidPage(
  textInput("name", "What's your name?"),
  textOutput("greeting")
)

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