Shiny render functions

[tylerlittlefield]

How do the shiny render functions work? I couldn't find any documentation on the topic. Below is my attempt:

library(shiny)
library(sortable)

ui <- fluidPage(
  sortable_output("sortable")
)

server <- function(input, output, session) {
  output$sortable <- render_sortable({
    rank_list(input_id = "test", labels = letters)
  })
}

shinyApp(ui, server)

[andrie]

This is actually a good question. With the hindsight of some distance from the project it's clear that the documentation is ambiguous.

The sortable_output() and render_sortable() functions are only useful if you want to create custom functions that wrap the sortable JS library.

In your case it seems you simply want to embed a rank_list() into your app. To do this, all you need is the rank_list() in your UI code, without any server code. Thus a rank_list() is somewhat similar to a radioButtons() or selectInput() - it's simply a mechanism to capture inputs.

Let me know if I misunderstood your question and you actually want to build a custom HTMLwidget using sortable.

[tylerlittlefield]

I think I was looking for update functions, something like updateRankListOuput or updateRankListInput. My particular use case it to allow users to rearrange the columns of their dataset, so the sortable labels need to be dynamic. I was able to achieve what I want with uiOutput:

library(shiny)

ui <- fluidPage(
  selectInput("data", "data", c("mtcars", "iris"), "mtcars"),
  uiOutput("sortable"),
  tableOutput("table")
)

server <- function(input, output, session) {
  rv <- reactiveValues(data = data.frame())

  observeEvent(input$data, {
    rv$data <- get(input$data)
  })

  observeEvent(input$sortable, {
    rv$data <- rv$data[input$sortable]
  })

  output$sortable <- renderUI({
    sortable::rank_list("", names(rv$data), "sortable")
  })

  output$table <- renderTable({
    rv$data
  })
}

shinyApp(ui, server)

[andrie]

That seems like a sensible approach for your use case. May I re-use this example in a vignette?

[tylerlittlefield]

Of course! ☺️

[andrie]

We fixed this in #67

[JacobBumgarner]

When testing this vignette locally, the options aren't able to be dragged after rendering them with renderUI. Is this a known issue?