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A Brochure Page

Source: R/brochure-fns-routr.R
page.Rd

A page is an url, a UI and a server function. Opening it starts a Shiny session of its own, separate from any other page of the app.

Usage

page(
  href,
  ui = tagList(),
  server = function(input, output, session) {
 },
  method = "GET",
  req_handlers = list(),
  res_handlers = list()
)

Arguments

href

The endpoint to serve the UI on. It can carry parameters, as in "/who/:id", which are read back with get_keys(). See details.

ui

The UI definition of the app (for example, a call to fluidPage() with nested controls).

If bookmarking is enabled (see enableBookmarking), this must be a single argument function that returns the UI definition.

server

A function with three parameters: input, output, and session. The function is called once for each session ensuring that each app is independent.

method

The HTTP method the page answers to. Defaults to "GET". A page on another method is unreachable if the app has a www/ directory at its root: Shiny mounts it as a static path on /, and httpuv answers anything that is not a GET or a HEAD from there with a 400 before R sees the request. Serve those files under a prefix instead, with shiny::addResourcePath().

req_handlers

a list of functions that can manipulate the req object. These functions should take req as a parameters, and return the req object (potentially modified), or an object of class httpResponse. If any of the req_handlers return an httpResponse, this response will be sent to the browser immediately, stopping any other code.

res_handlers

A list of functions that can manipulate the httpResponse object before it is send to the browser. Each function must take a res and req parameter.

Value

A brochure_page object, to be passed to brochureApp().

Details

Requests are matched against hrefs by the routr package, so an href is written the way routr writes a path:

  • "/contact" matches that path and nothing else.

  • ":name" matches exactly one segment and captures it, so "/who/:id" matches /who/colin but neither /who nor /who/colin/edit. Use several of them if you need to: "/pair/:a/:b".

  • "*" matches whatever is left, so "/files/*" matches /files/a/b/c. The captured value is named *1.

A trailing slash never matters: /contact and /contact/ are the same page.

Pages are tried in the order you passed them to brochureApp(), and the first match wins. That holds for the session a page opens as well, which is resolved on the path alone: the websocket handshake is a GET whatever method the page answers on, so two pages sharing an href run the server of the first one declared, whichever of them was served. That matters when two hrefs can match the same url: declared as page("/who/me") then page("/who/:id"), a request for /who/me gets the first; declared the other way round, the parameterised page catches it and the static one is never reached. Put the specific ones first.

See the routr documentation at https://routr.data-imaginist.com/ for the full path syntax.

See also

get_keys() to read the parameters of an href, and vignette("handlers") for req_handlers and res_handlers.

Examples

library(shiny)
page(
  href = "/page2",
  ui = tagList(
    h1("This is my second page"),
    plotOutput("plotb")
  )
)
#> $href
#> [1] "/page2"
#> 
#> $ui
#> <h1>This is my second page</h1>
#> <div class="shiny-plot-output html-fill-item" id="plotb" style="width:100%;height:400px;"></div>
#> 
#> $server
#> function (input, output, session) 
#> {
#> }
#> <environment: 0x5648cdf23600>
#> 
#> $method
#> [1] "get"
#> 
#> $req_handlers
#> list()
#> 
#> $res_handlers
#> list()
#> 
#> attr(,"class")
#> [1] "brochure_page" "list"