Render a ShinyTree asynchronously — renderTreeAsync • shinyTree

Like renderTree, but expr may also return a promise (see the promises package) of the tree, for a tree that is slow to build: with future, it is built in another process and the app stays responsive in the meantime. The tree is sent once the promise resolves; if it is rejected, the error is shown in place of the tree. An expression that returns a tree straight away works as it does in renderTree.

Usage

renderTreeAsync(expr, env = parent.frame(), quoted = FALSE)

Arguments

expr: An expression that returns a nested list or JSON, as for renderTree, or a promise of one.
env: The environment in which expr should be evaluated.
quoted: Is expr a quoted expression (with quote())? This is useful if you want to save an expression in a variable.

Value

A render function, to assign to output$<id> for a shinyTree with that id.

Details

Lazy loading (renderTree(lazy = TRUE)) is not available here.

Examples

if (interactive() && requireNamespace("future", quietly = TRUE)) {
  library(shiny)
  library(promises)
  library(future)
  plan(multisession)

  ui <- fluidPage(shinyTree("tree"))
  server <- function(input, output, session) {
    output$tree <- renderTreeAsync({
      future({
        Sys.sleep(2)  # a tree that is slow to build
        list(root = list(leaf = ""))
      })
    })
  }
  shinyApp(ui, server)
}

# See also the 16-async example:
if (interactive()) {
  shiny::runApp(system.file("examples/16-async", package = "shinyTree"))
}