Build Your Own Web Framework in Elixir by Aditya Iyengar

Author:Aditya Iyengar
Language: eng
Format: epub, pdf
Publisher: Packt Publishing Pvt Ltd
Published: 2023-05-18T00:00:00+00:00

Using EEx Smart Engine

EEx comes with the ability to override the engine that is being used to evaluate a template. The default engine used by EEx is EEx.SmartEngine. This module is built on top of the regular EEx.Engine but provides a way to speed up evaluation of a template by adding a special type of binding, assigns.

Let’s first take a look at an example:

./assigns.eex

<%= @a %> <%= @b %>

Now, let’s use the preceding template file to define a function in a module:

./module_b.ex

defmodule ModuleB do require EEx EEx.function_from_file(:def, :fun_b, "assigns.eex", [:assigns]) end

Updating our template and function to only take :assigns allows us to send different assigns without having to re-compile the template.

Now, let’s test out ModuleB.fun_b/1:

$ iex iex> Code.require_file("module_b.ex") [ {ModuleB, <<70, 79, 82, 49, 0, 0, 7, 68, 66, 69, 65, 77, 65, 116, 85, 56, 0, 0, 0,218, 0, 0, 0, 22, 14, 69, 108, 105, 120, 105, 114, 46, 77, 111, 100, 117, 108, 101, 66, 8, 95, 95, 105, 110, 102, 111, 95, ...>>} ] iex> ModuleB.fun_b(a: "Hello", b: "World") "Hello World
" iex> ModuleB.fun_b(a: "Hola", b: "World") "Hola World
"

This is super helpful to speed up the evaluation of templates while keeping the interface to use the templates simple and consistent. Phoenix uses a similar strategy to evaluate its templates.

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