Answer a component that asked the server for data — el_load

Element loads some components a piece at a time: a lazy tree its nodes' children, a lazy cascader its next column, a lazy tree table its rows' children. Upstream, a JavaScript function you write fetches them. Here the server does: the component asks through an input – input$<id>_load for a tree or table, input$<id>_lazy_load for a cascader – and waits until this function answers.

Usage

el_load_children(
  session = shiny::getDefaultReactiveDomain(),
  id,
  request,
  children = list(),
  reject = FALSE
)

Arguments

session: Shiny session; the current one by default, as for shiny::updateTextInput().
id: The component's ID (un-namespaced).
request: The question, as it arrived in input$<id>_load or input$<id>_lazy_load – or just its request number.
children: What to load. For a tree, nodes such as list(id =, label =, leaf = TRUE); for a cascader, options such as list(value =, label =, leaf = TRUE); for a table, rows, as a data.frame or a list. An empty list means there is nothing below.
reject: TRUE to answer that the load failed, Element Plus's reject(): a tree node stops spinning and can be loaded again when it is next expanded. A cascader or table takes it as nothing below.

Value

Called for its side effect; returns NULL invisibly.

Details

Each question carries a request number, so answers find their way back even when several are open at once; pass the question back whole.

Examples

if (interactive()) {
  library(shiny)
  ui <- el_page(el_tree(
    "files",
    lazy = TRUE,
    node_key = "id",
    props = list(isLeaf = "leaf")
  ))
  server <- function(input, output, session) {
    observeEvent(input$files_load, {
      q <- input$files_load
      dir <- if (q$level == 0) "~" else q$key
      entries <- list.files(dir, full.names = TRUE)
      el_load_children(
        id = "files",
        request = q,
        children = lapply(entries, function(f) {
          list(id = f, label = basename(f), leaf = !dir.exists(f))
        })
      )
    })
  }
  shinyApp(ui, server)
}