Shiny and shiny modules

Understand the basic behaviors

Some new technology related to shiny

Useful material

Book: Mastering Shiny

Get started

In an empty R script, type shiny, then a snippet should pop up to provide you with a template that contains to key components.

Tips

• run the entire script

Anatomy of a standard shiny app: 3 components

• ui function
• server function
• shinyApp function that combines the two parts above

# load the package
library(shiny)

# ui
ui <- page_fluid()

# server
server <- function(input, output, session){}

# combines the two
shinyApp(ui = ui, server = server)
# shinyApp(ui = app$ui, server = app$server)

Server functions

• inside ui, we have defined variables with inputID = x, outputID = 'scatterplot'; in the server these are called upon
• objects to be displayed should be saved to outputs$
• input values should be referred to with inputs$
• reactive objects should be built with render*() functions (renderPlot, renderText, renderTable etc)

Modules

Make the code more organized. Essentially wrapping components of UI / server into functions, then call the functions in the app.

• Very useful tutorial by Jonas Hagenberg: Structure your app: introduction to Shiny modules
• (More advanced) Talk by Eric Nantz: Effective use of Shiny modules in application development

Careful design: what does the module do? what is it trying to accomplish?

Input and return values: static or reactive inputs? complexity of return values; which outputs serve as inputs for other modules?

Module structure

This is how the shiny app with modules look like

# ui
ui <- page_fluid(
  
  # other UI elements
  # ...
  #
  # module UI
  module_UI(id = 'id_1')
  # can have more than one
)

# server
server <- function(input, output, session){
  
  # other server part
  # ...
  # module 
  module_server(id = 'id_1')
  # can have more than one
}

# combines the two
shinyApp(ui = ui, server = server)

Define the modules

# define the UI part
module_UI <- function(id){
  
  # namespaced id for input and output
  ns <- NS(id)
  
  # this is just a fancy list
  tagList(
    # your UI elements
  )
}

# define the server part
module_server <- function(id){
  moduleServer(
    id, 
    function(input, output, session){
      
    }
  )
  
}

Serverless shiny

Making use of webR

shinylive::export(from_here, to_there)

Use GHA to deploy the app

Public! No secrets