Controller

Bastion.Controller — structured request handling with automatic error recovery.

Controllers encapsulate request handling logic using the ActionResult type, which separates success (Ok) from failure (Error). This pattern, inspired by Phoenix controllers, lets handlers focus on business logic while error rendering is delegated to FallbackController.

Example:

fn show(conn : Conn) : Controller.ActionResult do
  let id_opt = Request.path_param(conn, "id")
  match id_opt do
  None      -> Controller.Error(404, "User not found")
  Some(id)  -> Controller.Ok(Response.json(conn, 200, "{\"id\":\"" ++ id ++ "\"}"))
  end
end

-- In the router handler:
fn show_handler(conn : Conn) : Conn do
  Controller.action(conn, fn c -> show(c))
end

Types

typeActionResultActionResult =#

Functions

fnactionaction(conn : Conn, handler : Conn -> ActionResult) : Conn#

Execute a controller action with automatic error handling.

Calls the handler function with the conn. If the handler returns Ok(conn),
the conn is returned as-is. If it returns Error(status, message), an HTML
error page is rendered using ErrorView.

Example:
  Controller.action(conn, fn c -> my_action(c))

fnjsonjson(conn : Conn, status : Int, body : String) : Conn#

Send a JSON response with the given status and body string.

The caller is responsible for serialising the body to a JSON string.

Example:
  Controller.json(conn, 200, Json.encode(data))

fnredirectredirect(conn : Conn, url : String) : Conn#

Send a redirect response (302 Found) to the given URL.

fnrenderrender(conn : Conn, status : Int, template : Conn -> String) : Conn#

Render HTML by calling a template function that receives the conn and returns an HTML string.

Example:
  Controller.render(conn, 200, fn c -> home_template(c))

fnrender_iolistrender_iolist(conn : Conn, status : Int, template : Conn -> IOList) : Conn#

Render HTML from a template function that returns an IOList (e.g. from ~H sigil). Converts the IOList to a string before sending.

Example:
  Controller.render_iolist(conn, 200, fn c -> ~H"<h1>Hello</h1>")

fnrender_iolist_okrender_iolist_ok(conn : Conn, template : Conn -> IOList) : Conn#

Convenience: render an IOList template with 200 OK status.

fnrender_okrender_ok(conn : Conn, template : Conn -> String) : Conn#

Convenience: render HTML with a 200 OK status.

Example:
  Controller.render_ok(conn, fn c -> home_template(c))

fntexttext(conn : Conn, status : Int, body : String) : Conn#

Send a plain text response with the given status and body.