Can you set assigns within a heex template to be used within a parent layout?

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3

You can send a Phoenix Component in the controller assigns and use it in the root layout.

In your controller:

defmodule NewPhoenixWeb.PageController do
  use NewPhoenixWeb, :controller

  def home(conn, _params) do
    render(conn, :home, my_root_component_content: apply(NewPhoenixWeb.Layouts, :custom_content_in_layout, [[]]))
  end

  def test(conn, _params) do
    render(conn, :home, my_root_component_content: apply(NewPhoenixWeb.Layouts, :another_custom_content_in_layout, [[]]))
  end
end

In your layouts.ex:

defmodule NewPhoenixWeb.Layouts do
  use NewPhoenixWeb, :html

  embed_templates "layouts/*"

  def custom_content_in_layout(assigns) do
    ~H"""
    <p>content one</p>
    """
  end

  def another_custom_content_in_layout(assigns) do
    ~H"""
    <p>content two</p>
    """
  end
end

Finally, in your root.html.heex (or any other layout file you want to use):

<div class="custom-content">
  <%= @my_root_component_content %>
</div>

Also, you can use slots:

defmodule NewPhoenixWeb.Layouts do
  slot :inner_block

  def my_root_component(assigns) do
    ~H"""
    <div>
      <%= render_slot(@inner_block) %>
    </div>
    """
  end
end

In root.html.heex:

<.my_root_component>
  <%= @my_root_component_content %>
</.my_root_component>

There’s a similar question here: Phoenix 1.7 and inversion of control to render a sidebar