Epoxy HTML Mustache Template

A Shiny output that uses mustache templating to render HTML. Mustache is a powerful template language with minimal internal logic. The advantage of ui_epoxy_mustache() is that all parts of the HTML can be templated -- including element attributes -- whereas ui_epoxy_html() requires that the dynamic template variables appear in the text portion of the UI. The downside is that the entire template is re-rendered (in the browser), each time that updated data is sent from the server -- unlike ui_epoxy_html(), whose updates are specific to the parts of the data that have changed.

Usage

ui_epoxy_mustache(
  id,
  ...,
  .file = NULL,
  .sep = "",
  .container = "epoxy-mustache"
)

ui_epoxy_whisker(
  id,
  ...,
  .file = NULL,
  .sep = "",
  .container = "epoxy-mustache"
)

Arguments

id

The ID of the output.

...

Character strings of HTML or htmltools::tags. All elements should be unnamed.

.file

A path to a template file. If provided, no other template lines should be included in ....

.sep

The separator used to concatenate elements in ....

.container

A character tag name, e.g. "div" or "span", or a function that returns an htmltools::tag().

Value

Returns a Shiny output UI element.

Functions

• ui_epoxy_whisker(): An alias for ui_epoxy_mustache(), provided because R users are more familiar with this syntax via the whisker package.

See also

ui_epoxy_html(), render_epoxy()

Other Mustache-style template functions: epoxy_mustache()

Examples

library(shiny)

ui <- fluidPage(
  fluidRow(
    style = "max-width: 600px; margin: 0 auto",
    column(
      width = 6,
      ui_epoxy_mustache(
        id = "template",
        h2(class = "{{heading_class}}", "Hello, {{name}}!"),
        "{{#favorites}}",
        p("Your favorite fruits are..."),
        tags$ul(HTML("{{#fruits}}<li>{{.}}</li>{{/fruits}}")),
        "{{/favorites}}",
        "{{^favorites}}<p>Do you have any favorite fruits?</p>{{/favorites}}"
      )
    ),
    column(
      width = 6,
      h2("Inputs"),
      textInput("name", "Your name"),
      textInput("fruits", "Favorite fruits", placeholder = "apple, banana"),
      helpText("Enter a comma-separated list of fruits.")
    )
  )
)

server <- function(input, output, session) {
  user_name <- reactive({
    if (!nzchar(input$name)) return("user")
    input$name
  })

  favorites <- reactive({
    if (identical(input$fruits, "123456")) {
      # Errors are equivalent to "empty" values,
      # the rest of the template will still render.
      stop("Bad fruits, bad!")
    }

    if (!nzchar(input$fruits)) return(NULL)
    list(fruits = strsplit(input$fruits, "\\s*,\\s*")[[1]])
  })

  output$template <- render_epoxy(
    name = user_name(),
    heading_class = if (user_name() != "user") "text-success",
    favorites = favorites()
  )
}

if (interactive()) {
  shiny::shinyApp(ui, server)
}
if (FALSE) { # rlang::is_interactive()
run_epoxy_example_app("ui_epoxy_mustache")
}