Elixir Cookbook

Book Image

Elixir Cookbook

By : Paulo Pereira

Book Image

Elixir Cookbook

By: Paulo Pereira

Overview of this book

Elixir Cookbook

Elixir Cookbook

Credits

About the Author

About the Author

About the Reviewers

About the Reviewers

www.PacktPub.com

www.PacktPub.com

Preface

Free Chapter

Command Line

Using the terminal to prototype and test ideas

Loading and compiling modules

Getting help and accessing documentation within IEx

Using Erlang from Elixir

Inspecting your system in IEx

Inspecting your system with Observer

Creating a simple application

Managing dependencies

Generating a supervised application

Generating umbrella applications

Managing application configuration

Creating custom Mix tasks

Data Types and Structures

Data Types and Structures

Understanding immutability

Adding and subtracting lists

Combining tuples into a list

Creating and manipulating keyword lists

Using pattern matching

Pattern matching an HTTPoison response

Creating a key/value store with a map

Mapping and reducing enumerables

Generating lazy (even infinite) sequences

Streaming a file as a resource

Strings and Binaries

Strings and Binaries

Joining strings

Splitting strings

Replacing string codepoints with patterns

Slicing strings with ranges

Using regular expressions

Combining operations with the |> operator

Creating a word list

Determining the word frequency in a text

Reading and writing metadata from MP3 files

Modules and Functions

Modules and Functions

Namespacing modules

Using module attributes as constants

Enforcing behaviors

Documenting modules

Using module directives

Using a module in the scripted mode

Defining functions with default arguments

Using guard clauses and pattern matching in function definitions

Processes and Nodes

Processes and Nodes

Sending messages between processes

Making code run on all available CPUs

Using tasks to perform multiple concurrent computations

Creating a stateful server process (messages with counters)

Using agents as an abstraction around states

Using an ETS table to share the state

Creating named nodes

Connecting nodes

Executing code in a different node

OTP – Open Telecom Platform

OTP – Open Telecom Platform

Implementing a GenServer

Expanding our server

Creating a supervisor

Using Observer to inspect supervisors and processes

Handling errors and managing exceptions

Packaging and releasing an OTP application

Deploying applications and updating a running system

Cowboy and Phoenix

Cowboy and Phoenix

Setting up Cowboy

Serving static files

Implementing a websocket handler

Creating a Phoenix application

Defining routes

Creating a controller

Creating views and templates

Implementing topics

Protecting the Phoenix app with SSL

Interactions

Using Redis and Postgres

Using OS commands from within Elixir

Getting Twitter data

Installation and Further Reading

Installation and Further Reading

Installing Elixir

Installing PostgreSQL

Installing Redis

Some useful links

Index

Customer Reviews

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1 star

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Using module attributes as constants

Elixir supports the definition of module attributes using the @ syntax. There are a few reserved module attributes: @moduledoc, @doc, @behaviour, and @before_compile. We will focus on some of them in the next two recipes.

In this recipe, we will use module attributes as constants and access them inside functions.

Note

Module attributes can only be defined outside functions and can be defined more than once in a module.

How to do it…

To use module attributes as constants, follow these steps:

Create a new constants.ex module and add the following code:

defmodule Constants do
  @name "Bill"
  @age 22

  def function_one do
    IO.puts("#{@name} is #{@age} years old.")
  end

  @name "Joe"
  def function_two do
    IO.puts("#{@name} is #{@age+1} years old.")
  end
end

Start an IEx session in the same directory where you saved constants.ex:
```
> iex constants.ex
```
Tip
Instead of starting IEx and then loading and compiling the module, it is possible to indicate the name...