title	author	date	output
Shiny Module Learning	Brian S Yandell	May 19, 2016	html_document

This project is about learning how to use Shiny modules. I developed these as my modules were crashing, and I wanted to break down into simple steps. See links below for official resources.

• 2016 Shiny Developer Conference
  • see talk by Garrett
  • Conference Material
  • Conference Material
• Modularizing Shiny app code (Joe Cheng article)
• Shiny Gallery
  • Update Input
  • Dynamic UI
  • Conditional Panel
  • Progress Bar

The folder has several R scripts. Latest material is in the oldfaithful folder. See also Conference Material on Modules. These were adapted from and inspired by Garrett's talk. Each file is a complete shiny app that can be run.

• simple.R simple Shiny script using sliderInput() and textOutput()
• module.R simple.R modified to have key components in Shiny module
• nested.R example nesting two modules
• *_renderUI.R examples using renderUI() in server and uiOutput() in ui
• *_observeEvent.R examples using observeEvent() for actionButton()
• *_observe.R examples using observe() for checkboxInput()
• *_renderUI_*.R examples using renderUI and observe() or observeEvent()

Key things to notice about namespace use for modules:

• module UI and server must use same id
  • sliderTextUI("module") # in ui function
  • callModule(sliderText, "module", ...) # in server function
• module server needs session as third argument
• return argument from module server (if any) must be reactive()
• module UI needs two nameserver components
  • ns <- NS(id) # to create namespace ID function
  • tagList( # tag list to wrap UI entries
  • sliderInput(ns("slider"), ...) # to use namespace ID
  • ) # ends tag list
• module server has no special arrangements except in use of renderUI()
  • ns <- server$ns # to access namespace ID function
  • output$set_slider <- renderUI({
  • sliderInput(ns("slider"), ...) # to use namespace Id
  • })
• module server has no special arrangements for update*Input
  • updateSliderInput(server, "slider", ...)
  • used in observe() and observeEvent()
• conditionalPanel does not work as expected with modules
  • see worked examples in oldfaithful folder
  • condition argument is interpreted by javascript
  • input elements for a module namespace require care with JS
  • see Rstudio Shiny issue or TB Adams gist for helpful solutions