This is an implementation of EEx.Engine that injects Drab.Live behaviour.

It parses the template during compile-time and inject Drab markers into it. Because of this, template must be a proper HTML. Also, there are some rules to obey, see limitations below.

Limitations

Avalibility of Assigns

To make the assign avaliable within Drab, it must show up in the template with “@assign” format. Passing it to render in the controller is not enough.

Also, the living assign must be inside the <%= %> mark. If it lives in <% %>, it will not be updated by Drab.Live.poke/2. This means that in the following template:

<% local = @assign %>
<%= local %>

poking @assign will not update anything or, if @assign was not declared somewhere else, it will raise the assign not found exception*.

Properties

Property must be defined inside the tag, using strict @property.path.from.node=<%= expression %> syntax. One property may be bound only to the one expression, no apostrophe or double quote allowed.

<button @hidden=<%= @hidden %> ...>
<button @style.backgroundColor=<%= my_color_function(@button1) %> ...>

Please notice that the full path to the property is allowed here, in this case the function is bound to node.style.backgroundColor.

Attributes

The attribute must be well defined, and you can’t use the expression as an attribute name.

The following is valid:

<button class="btn <%= @button_class %>">
<a href="<%= build_href(@site) %>">

But following constructs are prohibited:

<tag <%="attr='" <> @value <> "'"%>>
<tag <%=build_attr(@name, @value)%>>

The above will compile (with warnings), but it will not be correctly updated with Drab.Live.poke.

The tag name can not be build with the expression.

<<%= @tag_name %> attr=value ...>

Nested expressions are not valid in the attribute pattern. The following is not allowed:

<tag attribute="<%= if clause do %><%= expression %><% end %>">

Do a flat expression instead:

<tag attribute="<%= if clause, do: expression %>">

Scripts

Tag name must be defined in the template as <script>, and can’t be defined with the expression.

Nested expressions are not valid in the script pattern. The following is not allowed:

<script>
  <%= if clause do %>
    <%= expression %>
  <% end %>>
</script>

Do a flat expression instead:

<script>
  <%= if clause, do: expression %>
</script>