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Elixir Cookbook

By : Paulo Pereira

4.5 (2)

Elixir Cookbook

4.5 (2)

By: Paulo Pereira

Overview of this book

This book is intended for users with some knowledge of the Elixir language syntax and basic data types/structures. Although this is a cookbook and no sequential reading is required, the book’s structure will allow less advanced users who follow it to be gradually exposed to some of Elixir’s features and concepts specific to functional programming. To get the most out of this book, you need to be well versed with Erlang.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Conventions

Reader feedback

Customer support

Free Chapter

1. Command Line

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Interactions

Introduction

Using Redis and Postgres

Using OS commands from within Elixir

Getting Twitter data

A. Installation and Further Reading

A. Installation and Further Reading

Installing Elixir

Installing PostgreSQL

Installing Redis

Some useful links

Index

Index

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Getting help and accessing documentation within IEx

Documentation is a first-class citizen in the Elixir ecosystem, so it comes as no surprise that IEx provides convenient ways to access documentation and get help without the need to leave an IEx session.

This recipe exemplifies the use of the defined help functions.

How to do it…

We will follow these steps to get help and access documentation in an IEx session:

Enter h inside a running IEx session to see the help options related to the use of IEx helpers, as shown in this screenshot:
If we wish, for instance, to get information regarding the c/2 function, we type h(c/2), as shown in the following screenshot:
Accessing a module documentation is done by invoking h(ModuleName). In the next screenshot, we access documentation related to Enum:
Getting information about a specific function inside a module is also possible by invoking h(ModuleName.function_name). The following screenshot shows the documentation for Enum.map:

How it works…

When we define modules, it is possible to use the @moduledoc and @doc annotations to define documentation related to the whole module or to a specific function in that module.

IEx parses the documentation defined with these annotations and makes it available in a convenient way so that there's no need to leave the session when help or some more information is needed.

IEx itself has several helper functions defined (refer to the first screenshot of this recipe), and among them, we find h/0 and h/1.

Note

It is common to refer to functions by their name followed by / and a number indicating the number of arguments that function takes. Therefore, h/0 is a function named h that takes 0 arguments, and h/1 is the same h function but with 1 argument.

There's more…

There are several defined functions that allow accessing information on function specifications and types (if defined). To learn more, you can use s/1 and t/1.

As an example, to get information on the types defined for the Enum module, we would use t(Enum), and to get information on the specifications, we would use s(Enum).

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