What is the ~E sigil in the Drab tutorial?

Zesky665

Hi,

I’m going through the examples on the drab page. In the ‘chat example’ section, in the code example.

defhandler update_chat(socket, sender) do
  nick = get_store(socket, :nickname, "Anonymous")
  html = ~E"<strong><%= nick %>:</strong> <%= message %><br>" |> safe_to_string()
  broadcast_insert socket, "#chat", :beforeend, html
  set_prop socket, this(sender), value: ""
  broadcast_js socket, "document.querySelector('#chat').scrollTop = 
  document.querySelector('#chat').scrollHeight"`
end

On the third line, the one with html, a sigil ~E is used. I don’t know what this does, and it doesn’t show up in the elixir docs or in the page source code. Anyone know what this is?

18 comments

/phoenix #sigils #drab

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2019-02-18 16:15:18 UTC

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yurko

That comes from Phoenix HTML package: “Provides ~E sigil with HTML safe EEx syntax inside source files”.

Post #1

grych

Creator of Drab

It is important to use safe when you build html from the outside source, like inputs. Future versions of Drab will take safe directly, so you’ll not have to add safe_to_string/1.

Post #2

marat

Trying chat example as well.
Getting
page_commander.ex:13: undefined function safe_to_string/1

Post #3

grych

Creator of Drab

import Phoenix.HTML

in the commander, or just call Phoenix.HTML.safe_to_string directly.

Post #4

marat

Tried to call module.function, that gave page_commander.ex:14: undefined function sigil_E/2.
Now,
page_commander.ex:16: undefined function message/0

it’s the 3rd line in

  defhandler update_chat(socket, sender) do
    nick = get_store(socket, :nickname, "Anonymous")
    html = ~E"<strong><%= nick %>:</strong> <%= message %><br>" |> safe_to_string()

Post #5

Zesky665

You need to define message within the function. It’s currently not defined and the program assumes its some undefined function.

What I did was get the message value from the sender.

message = sender["value"]

Or something similar, I’ll post the actual code when I get the chance.

Post #6

grych

Creator of Drab

Yes, I made a mistake when copying the code to the html, will be added soon.
message = sender["value"] is correct.

Post #7

marat

Yes, this works:

  defhandler update_chat(socket, sender) do
    nick = get_store(socket, :nickname, "Anonymous")
    message = sender["value"]
    html = ~E"<strong><%= nick %>:</strong> <%= message %><br>" |> safe_to_string()
...

Post #8

marat

@grych another issue with chat:

defmodule AppWeb.PageCommander do
  use Drab.Commander #, modules: [Drab.Presence]
  import Phoenix.HTML
  import Drab.Presence

gives error:

** (CompileError) lib/olist_no_brunch_web/commanders/page_commander.ex:4: module Drab.Presence is not loaded and could not be found
    (stdlib) erl_eval.erl:677: :erl_eval.do_apply/6

I have in config:

config :drab, :default_modules, [Drab.Live, Drab.Element, Drab.Waiter, Drab.Modal, Drab.Presence]
config :drab, :presence, id: [store: :nickname, session: :nickname] 
config :drab, :presence, endpoint: AppWeb.Endpoint

and still no luck :((

Post #9