Simple counter using reactiveValues() in R Shiny - An example

DESCRIPTION

Title: reactiveValues() function
Description: With reactiveValues(), you can create your own reactive values. reactiveValues() Creates a list of objects that can be manipulated within a reactive context (within observer or observerEvent with dependency on changes in certain input or state of an object). reactiveValues() objects are not reactive themselves and do not re-execute themselves when input value changes unlike reactive objects. Powered by R, Shiny, and RStudio.
License: GPL-3
Author: Abhinav Agrawal
DisplayMode: Showcase
Tags: R, R Shiny,reactiveValues(), observeEvent()
Type: Shiny

server.r

library(shiny)
shinyServer(
  function(input, output, session) {
    counter <- reactiveValues(countervalue = 0) # Defining & initializing the reactiveValues object
    
    observeEvent(input$add1, {
      counter$countervalue <- counter$countervalue + 1     # if the add button is clicked, increment the value by 1 and update it
    })
    observeEvent(input$sub1, {
      counter$countervalue <- counter$countervalue - 1  # if the sub button is clicked, decrement the value by 1 and update it
    })
    observeEvent(input$reset, {
      counter$countervalue <- 0                     # if the reset button is clicked, set the counter value to zero
    })
    output$count <- renderText({
      paste("Counter Value is ", counter$countervalue)   # print the latest value stored in the reactiveValues object
    })

    
  }
  
)

ui.r

library(shiny)
shinyUI(
  fluidPage(
    tags$b("Simple counter using reactiveValues() - An example"),
    br(),
    actionButton("add1", "+ 1"),
    actionButton("sub1", "- 1"),
    actionButton("reset", "set to 0"),
    br(),
    textOutput("count")
  )
  
)