Gain insights into metaprogramming in Elixir. Delve into macros and discover how to elevate your coding skills, creating powerful libraries with concise, efficient code.

_Metaprogramming Elixir by The Pragmatic Programmer_468 x 60 copy.png

elixir.tar.gz

elixir

elixir-testing

elixir-copy

Get introduced to the concept of metaprogramming. Learn how to level up your programming skills by discovering the full potential of the macro system in Elixir. Understand the ins and outs of metaprogramming at a fundamental level and write incredible libraries by doing more with less code.

Metaprogramming in Elixir


Elixir allows us to set a special module attribute, `@before_compile`, to notify the compiler that an extra step is required just before compilation is finished. The `@before_compile` attribute accepts a module argument where a `__before_com- pile__/1 `macro must be defined. This macro is invoked just before compilation  to perform a final bit of code generation. Let’s apply this hook to fix our `test` macro. 



![](/api/collection/10370001/5074130048647168/page/5571214875033600/image/5530254539489280?page_type=collection_lesson)

## Using the `before_compile` module attribute
Let's update our `Assertion` module with these `@before_compile` hooks and test it using the following commands:
``` elixir
iex> c "assertion.exs"
# Output: [Assertion.Test, Assertion]
iex> c "math_test_step1.exs" 
# Output: [MathTest]
iex> MathTest.run 
# Output: 
# Running the tests(["integers can be added and subtracted": 
# "integers can be added and subtracted"]) 
# :ok
```

# Using the `before_compile` module attribute
Let's update our `Assertion` module with these `@before_compile` hooks and test it using the following commands:
``` elixir
iex> c "assertion.exs"
# Output: [Assertion.Test, Assertion]
iex> c "math_test_step1.exs" 
# Output: [MathTest]
iex> MathTest.run 
# Output: 
# Running the tests(["integers can be added and subtracted": 
# "integers can be added and subtracted"]) 
# :ok
```

Learn to fix the test macro using compile-time hooks.

Introduction

The Language of Macros

Extending Elixir with Metaprogramming

Advanced Compile-Time Code Generation

Code Generation from Git API

How to Test Macros

Create an HTML Domain-Specific Language

With Great Power Comes Great Responsibility (and Fun!)

Compile-Time Hooks

The `before_compile` module attribute

Using the `before_compile` module attribute

Code Generation from Git API

Compile-Time Hooks

The before_compile module attribute

Using the before_compile module attribute

The `before_compile` module attribute

Using the `before_compile` module attribute