Tips and Tricks

Just a few assorted tricks of the trade for doing "real-world" work with Sugar. The examples provided assume you've created a Sugar project called YourProject by following the Getting Started guide.

If you'd like to contribute something you've stumbled upon, feel free to send in a pull request with your additions; we're happy to include all sort of community tips/tricks.


The best way to go about this is to use Plug.Parsers and Plug.Upload. In your router (lib/your_project/router.ex):

defmodule YourProject.Router do
  use Sugar.Router

  # ... other router stuff

  plug Plug.Parsers, parsers: [ Plug.Parsers.URLENCODED,
                                Plug.Parsers.MULTIPART ]

  # ... other router stuff

  get  "/uploads", YourProject.Controllers.Upload, :index
  post "/uploads", YourProject.Controllers.Upload, :create  # for example

Then, in your controller (lib/your_project/controllers/upload.ex):

defmodule YourProject.Controllers.Main do
  use Sugar.Controller

  def index(conn, _) do
    conn |> render

  def create(conn, _) do
    # For example:
    %Plug.Upload{filename: filename, path: path} = conn.params["file"]
    path |>! |> do_something(filename)  # or whatever
    conn |> redirect("/uploads")                  # or whatever

And finally, in your view (lib/your_project/views/upload/index.html.eex):

  <form enctype="multipart/form-data" action="/uploads" method="post">
    <input type="file" name="file">
    <input type="submit">

Phoenix Compatibility

Both Sugar and Phoenix build on top of Plug, so there's not a whole lot that needs to be done; most of the time, things should Just Work™. If they don't (and a workaround isn't described here), feel free to submit a bug.


If your Sugar controller needs to use a plug that expects to be used in a Phoenix controller (notably, one that acts on Phoenix controller actions), the fix is pretty simple. In your controller (lib/your_project/controllers/phoo_bar.ex):

defmodule YourProject.Controllers.PhooBar do
  use Sugar.Controller

  plug :phoenix_compat
  plug SomePlugThatExpectsPhoenixActions

  # ... other controller stuff

  def phoenix_compat(conn, _) do
    private = conn.private |> Map.merge(%{
      phoenix_controller: conn.private[:controller],
      phoenix_action:     conn.private[:action] })

    %Plug.Conn{ conn | private: private }


Sugar ships with a Sugar.Plugs.EnsureAuthenticated plug that'll (unless configured with a handler that does something else) redirect clients to a login page if the client isn't currently logged in. Using it is dead-simple.

First, in your router (lib/your_project/router.ex), assuming that you're using an ETS-based session store (you should probably roll your own or go with encrypted cookies for production apps, at least per Plug's own documentation):

defmodule YourProject.Router do
  use Sugar.Router

  # ... other router stuff

  # Uncomment the following line for session store
  plug Plug.Session, store: :ets, key: "sid", secure: true, table: :session

  # ... other router stuff

  # This can be anything that brings the user to a login page
  get "/login", YourProject.Controllers.Login, :new

Next, you'll want to create an Ecto repo (like YourProject.Repos.Main) and a user model (like YourProject.Models.User), since Sugar.Plugs.EnsureAuthenticated assumes these to exist and behave like Ecto repos/models (but doesn't really care, so long as YourProject.Models.User is a struct with an :id field and YourProject.Repos.Main has a get/2 function that returns such a struct).

Finally, in the controller that you want to restrict (lib/your_project/controllers/foo_bar.ex):

defmodule YourProject.Controllers.FooBar do
  use Sugar.Controller

  plug Sugar.Plugs.EnsureAuthenticated

  def some_action(conn, _) do
    user = conn.assigns[:current_user]          # %YourProject.Models.User{ ... }
    conn |> render(current_user: current_user)  # or something

Now, users will only be able to access that controller action if they're logged in (otherwise, they'll be redirected to the /login route). See the Sugar.Plugs README for more details.

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