Book Image

Elixir Cookbook

By : Paulo Pereira
Book Image

Elixir Cookbook

By: Paulo Pereira

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Elixir Cookbook
Paulo Pereira
Feb, 2015 | 236 pages
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Table of Contents (16 chapters)
Elixir Cookbook
Elixir Cookbook
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Command Line
Command Line
Introduction
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
2
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
3
Strings and Binaries
Strings and Binaries
Introduction
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
4
Modules and Functions
Modules and Functions
Introduction
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
5
Processes and Nodes
Processes and Nodes
Introduction
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
6
OTP – Open Telecom Platform
OTP – Open Telecom Platform
Introduction
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
7
Cowboy and Phoenix
Cowboy and Phoenix
Introduction
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
8
Interactions
Interactions
Introduction
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
Index

Using Erlang from Elixir

Elixir code runs in the Erlang VM. The ability to invoke Erlang code from within Elixir allows the use of resources from the entire Erlang ecosystem, and since Elixir code is compiled to the same byte code as Erlang code, there is no performance penalty.

It is also possible to include in an Elixir application the Erlang code that is already compiled.

If you take a closer look, the files we compile in IEx sessions have the .beam extension, and that's exactly the same format Erlang's compiled code gets transformed into.

Getting ready

To use Erlang code in Elixir, we start a new IEx session.

How to do it…

These are some examples of how to invoke Erlang code from Elixir:

  1. Erlang's Application module defines a function named which_applications. This function returns a list of applications being executed in an Erlang VM. This is the way to use this function from Elixir:

    iex(1)> :application.which_applications

    Note

    The Erlang code would be application:which_applications().

  2. To get information on any Erlang module, there is a function named module_info. To know more about the erlang module, we enter this:

    iex(2)> :erlang.module_info

    Note

    The Erlang code would be erlang:module_info().

How it works…

In Elixir, Erlang modules are represented as atoms. Functions in these modules are invoked in the same way as any Elixir function.

Note

In Elixir, the atom type is used as an identifier for a given value. In Ruby, the equivalent of the atom is known as the symbol.

There's more…

Existing Erlang libraries can be included in Elixir applications, widening the available options. It is also possible to choose an Erlang implementation of a module over Elixir's.

The Elixir standard library has a List module defined. The Erlang counterpart is lists.

If we wish to get the last element of a list, we could use both modules:

  • We can use Elixir's List module like this:

    List.last([1,2,3])

  • We can use Erlang's lists module in this manner:

    :lists.last([1,2,3])

    Note

    The Erlang code for this operation is lists:last([1,2,3]).

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