scrivener_phoenix

Helper to render a Scrivener pagination for phoenix.

Features

Inverted pagination

In a standard pagination, the first page contains the latest content:

« First ‹ Prev ... 2 3 4 5 6 7 8 9 10 ... Next › Last »

This package provides an option for an inverted pagination where the first page contains the oldest content:

« Last ‹ Next ... 10 9 8 7 6 5 4 3 2 ... Prev › First »

Installation

The package can be installed by adding scrivener_phoenix to your list of dependencies in mix.exs:

def deps do
  [
    # ...
    {:scrivener_ecto, "~> 2.7"},
    {:scrivener_phoenix, "~> 0.3.2"},
  ]
end

The docs can be found at https://hexdocs.pm/scrivener_phoenix.

Configuration

Configure scrivener_phoenix in your_app/config/config.exs:

config :scrivener_phoenix,
  left: 0,
  right: 0,
  window: 4,
  outer_window: 0,
  live: false,
  inverted: false,
  param_name: :page,
  merge_params: false,
  display_if_single: false,
  template: Scrivener.Phoenix.Template.Bootstrap4

(these are the defaults and can be omitted)

• left (default: 0): display the left first pages
• right (default: 0): display the right last pages
• window (default: 4): display window pages before and after the current page (eg, if 7 is the current page and window is 2, you'd get: 5 6 7 8 9)
• outer_window (default: 0), equivalent to left = right = outer_window: display the outer_window first and last pages (eg valued to 2: « First ‹ Prev 1 2 ... 5 6 7 8 9 ... 19 20 Next › Last » as opposed to left = 1 and right = 3: « First ‹ Prev 1 ... 5 6 7 8 9 ... 18 19 20 Next › Last »)
• live (default: false): true to generate links with Phoenix.LiveView.Helpers.live_patch/2 instead of Phoenix.HTML.Link.link/2
• inverted (default: false): see Inverted pagination above
• display_if_single (default: false): true to force a pagination to be displayed when there only is a single page of result(s)
• param_name (default: :page): the name of the parameter generated in URL (query string) to propagate the page number
• merge_params (default: false): true to copy the entire query string between requests, false to ignore it or a list of the parameter names to only reproduce
• template (default: Scrivener.Phoenix.Template.Bootstrap4): the module which implements Scrivener.Phoenix.Template to use to render links to pages
• symbols (default: %{first: "«", prev: "‹", next: "›", last: "»"}): the symbols to add before or after the label for the first, previous, next and last page (nil or "" for none)
• labels (default: %{first: dgettext("scrivener_phoenix", "First"), prev: dgettext("scrivener_phoenix", "Prev"), next: dgettext("scrivener_phoenix", "Next"), last: dgettext("scrivener_phoenix", "Last")}): the texts used by links to describe the first, previous, next and last page

Usage

In your Repo (the file is probably lib/your_app/repo.ex), add use Scrivener

In concerned views, add:

import Scrivener.PhoenixView

Or, to be global, add it to lib/your_app_web.ex:

defmodule YourAppWeb do
  # ...
  def view do
    quote do
      # ...
      import Scrivener.PhoenixView # <= add this line
    end
  end
  # ...
end

(a third solution is to directly use Scrivener.PhoenixView.paginate instead of just paginate in your templates)

In your context, the resultset of your query is paginated with scrivener:

defmodule MyApp.Blog do
  def posts_at_page(page) do
    MyApp.Post
    |> order_by(:created_at)
-   |> Repo.all()
+   |> Repo.paginate(page: page) # <= this line is your scrivener pagination
  end
end

Then, in your controller, assign it to the view:

defmodule MyAppWeb.BlogController do
  # ...

  def index(conn, params) do
    posts =
      params
      |> Map.get("page", 1) # <= extract the page number from params if present else default to first page
      |> Blog.posts_at_page()

    conn
    |> assign(:posts, posts)
    # ...
    |> render(:index)
  end

  # ...
end

Then, in your template, you just have to call the paginate helper:

<%= paginate(@conn, @posts, route_function, route_params) %>

Where:

• route_function is the helper (YourAppWeb.Router.Helpers.*_url or YourAppWeb.Router.Helpers.*_path) - don't forget to add the & and the /arity. Example: &MyBlogWeb.Router.Helpers.blog_path/3
• route_params is a list of parameters passed to route_function excepted the conn (%Plug.Conn{}). This list should at least contains the action. Example: [:index]

NOTES:

By "default", scrivener_phoenix will simply propagate the page number in the query string (eg: /blog?page=1).

For this route:

defmodule MyBlogWeb.Router do
  scope "/" do
    # ...
    get "/", MyBlogWeb.PostController, :index
    # ...
  end
end

You have to paginate this way:

<%= paginate(@conn, @posts, &MyBlogWeb.Router.Helpers.blog_path/3, [:index]) %>

The /3 arity stands for:

1. the conn
2. the action (:index)
3. the additionnal (and facultative) parameters to add in query string (where the page parameter will be injected)

Because Phoenix defines the corresponding path helper this way:

def blog_path(conn_or_endpoint, action = :index, query_params \\ [])

But the page parameter can also be included in the path of the URL instead of the query string (eg /blog/page/1), like this:

defmodule MyBlogWeb.Router do
  scope "/" do
    # ...
    get "/page/:page", MyBlogWeb.PostController, :index, as: :page
    # ...
  end
end

And you paginate as follows:

<%= paginate(@conn, @posts, &MyBlogWeb.Router.Helpers.blog_page_path/4, [:index]) %>

The arity becomes /4 with the additionnal :page parameter:

1. the conn
2. the action (:index)
3. the page
4. the additionnal (and facultative) parameters to add in query string

In this case, the corresponding path helper is defined as:

def blog_page_path(conn_or_endpoint, action = :index, page, query_params \\ [])

TL;DR: for arity, add 3 to the length of the list you pass as parameters if page number is a parameter to your route else 2 (and the page number will be part of the query string)

Of course you can use your own functions as callback, eg: <%= paginate @conn, @posts, fn conn, args -> MyBlogWeb.Router.Helpers.blog_path(conn, :index, args) end %> or:

defmodule SomeModule do
  def comment_index_url(conn, post, page, args) do
    MyBlogWeb.Router.Helpers.blog_post_comment_page_url(conn, :index, post, page, args)
  end
end

With <%= paginate(@conn, @comments, &SomeModule.comment_index_url/3, [@post]) %> in the template.

Note that the conn (or endpoint module's name) remains the first argument and the Keyword-list for the query string parameters the very last.

Note regarding Phoenix >= 1.7 and verified routes

To still use route helpers change use Phoenix.Router, helpers: false to use Phoenix.Router, helpers: true in your_app/lib/your_app_web.ex

LiveView: dealing with live views

In order to avoid liveview reloading, we need to handle page changes with handle_params/3 callback but without triggering a full (re)mount/3. To do so, pagination links have to be generated by calling Phoenix.LiveView.Helpers.live_patch/2 instead of the "regular" Phoenix.HTML.Link.link/2. Since you may want to share a same template for dead and live views, a live option has been introduced to know which of these two has to be called.

So, comparatively to a dead view, only 2 changes are required:

1. the first parameter of Scrivener.PhoenixView.paginate/5, usually @conn, becomes @socket
2. add live: true as option to Scrivener.PhoenixView.paginate/5 but as of scrivener_phoenix 0.3.2 it should be automatically set for you

Example:

  defp to_tuple(socket = %Phoenix.LiveView.Socket{}, atom)
    when is_atom(atom)
  do
    {atom, socket}
  end

  @impl Phoenix.LiveView
  def mount(params, session, socket) do
    # in mount, we load the first page by default
    socket
    |> assign(:posts, Blog.posts_at_page(1)) # see the module MyApp.Blog above if needed
    # ...
    |> to_tuple(:ok)
  end

  @impl Phoenix.LiveView
  def handle_params(params, _uri, socket) do
    # here, we fetch the page number from params to load and update the posts assign
    posts =
      params
      |> Map.get("page", 1)
      |> Blog.posts_at_page()

    socket
    |> assign(:posts, posts)
    |> to_tuple(:noreply)
  end

  # NOTE: this callback can be replaced by a .html.heex template
  @impl Phoenix.LiveView
  def render(assigns) do
    ~H"""
    ...

    <%#
      For:

      live "...", BlogPostLive, :index

      In the router (lib/your_app_web/router.ex, report to the output of the command `mix phx.routes` if you are not sure about the path helper function's name).
    %>
    <%= paginate(@socket, @posts, &Routes.blog_post_path/3, [:index], live: true) %>

    ...
    """
  end

push_patch (and/or propagating initial parameters in LV)

LiveViews doesn't record the actual query string (Phoenix.LiveView.get_connect_params/1 can't be called after mount) so you have to handle these parameters by assigning them into an assign and reinject them as :params options. Example:

  def handle_event/handle_info(...) do
    new_params = ...

    socket
    |> assign(:pagination_params, new_params)
    |> push_patch(to: Routes.user_path(socket, :show, user, new_params))
    # or
    #|> push_patch(to: ~p"/user/#{@user}?#{new_params}")
    |> to_tuple(:noreply)
  end

Then in your template:

<%= paginate(@conn, @posts, &Routes.user_path/4, [:show, @user], [params: @pagination_params]) %>