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Build Your Own Web Framework in Elixir

You're reading from   Build Your Own Web Framework in Elixir Develop lightning-fast web applications using Phoenix and metaprogramming

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Product type Paperback
Published in Jun 2023
Publisher Packt
ISBN-13 9781801812542
Length 274 pages
Edition 1st Edition
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Author (1):
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Aditya Iyengar Aditya Iyengar
Author Profile Icon Aditya Iyengar
Aditya Iyengar
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Toc

Table of Contents (15) Chapters Close

Preface 1. Part 1: Web Server Fundamentals
2. Chapter 1: Introducing the Cowboy Web Server FREE CHAPTER 3. Chapter 2: Building an HTTP Server in Elixir 4. Part 2: Router, Controller, and View
5. Chapter 3: Defining Web Application Specifications Using Plug 6. Chapter 4: Working with Controllers 7. Chapter 5: Adding Controller Plugs and Action Fallback 8. Chapter 6: Working with HTML and Embedded Elixir 9. Chapter 7: Working with Views 10. Part 3: DSL Design
11. Chapter 8: Metaprogramming – Code That Writes Code 12. Chapter 9: Controller and View DSL 13. Chapter 10: Building the Router DSL 14. Index

Code injection using macros

We learned that we can use Code.eval_quoted/3 to dynamically add behavior to a module, but Elixir provides a cleaner and more consistent way of doing this, using macro.

Code.eval_quoted/3 allows us to inject code using a set of variable bindings and an environment. macro, on the other hand, allows us to define a set of quoted literals at the time of their compilation and evaluate the expressions, by simply invoking it like a function inside another module. A macro can be defined by using defmacro/2, which itself is a macro.

To understand the preceding distinction better, let us use macro to implement the same BehaviorInjector module and inject behavior in the TestSubject module:

behavior_injector.ex

defmodule BehaviorInjector do
  defmacro define_hello do
    quote do
      def hello, do: IO.puts "Hello world!"
    end
  end
end

In the preceding...

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