Purpose

This tutorial introduces the basics of using MessagePack Ruby to serialize and deserialize Ruby objects.

References

Prerequisites

  • Basic knowledge of Ruby

  • Ruby 2.7 or higher

Installing the gem

Add to your Gemfile:

gem 'messagepack'

Or install directly:

gem install messagepack

Your first serialization

Basic pack and unpack 

require 'messagepack'

# Pack some data
data = { message: "Hello, MessagePack!" }
binary = Messagepack.pack(data)

# Inspect the binary (non-printable characters escaped)
puts binary.inspect
# => "\\x81\\xA7message\\xB4Hello, MessagePack!"

# Unpack the data
result = Messagepack.unpack(binary)
puts result.inspect
# => {"message"=>"Hello, MessagePack!"}

Working with different types 

# Numbers
Messagepack.pack(42)          # Integer
Messagepack.pack(3.14)        # Float
Messagepack.pack(-100)        # Negative integer

# Strings and symbols
Messagepack.pack("hello")     # String
Messagepack.pack(:world)      # Symbol (serialized as string)

# Collections
Messagepack.pack([1, 2, 3])   # Array
Messagepack.pack({a: 1})      # Hash

# Special values
Messagepack.pack(nil)         # Nil
Messagepack.pack(true)        # Boolean true
Messagepack.pack(false)       # Boolean false

Working with IO

Writing to a file 

data = { name: "Alice", age: 30, skills: ["Ruby", "Python"] }

# Write to file
File.open("data.msgpack", "wb") do |file|
  file.write(Messagepack.pack(data))
end

Reading from a file 

# Read from file
data = File.read("data.msgpack", encoding: Encoding::BINARY)
result = Messagepack.unpack(data)
# => {"name"=>"Alice", "age"=>30, "skills"=>["Ruby", "Python"]}

Using IO directly 

# Unpack can read from IO directly
File.open("data.msgpack", "rb") do |file|
  result = Messagepack.unpack(file)
end

Practical example: Configuration file

Create a simple configuration system using MessagePack:

require 'messagepack'

class Config
  def initialize(path)
    @path = path
    @data = load
  end

  def [](key)
    @data[key]
  end

  def []=(key, value)
    @data[key] = value
    save
  end

  private

  def load
    if File.exist?(@path)
      Messagepack.unpack(File.read(@path, encoding: Encoding::BINARY))
    else
      {}
    end
  end

  def save
    File.write(@path, Messagepack.pack(@data))
  end
end

# Usage
config = Config.new("config.msgpack")
config[:database] = { host: "localhost", port: 5432 }
config[:debug] = true

puts config[:database][:host]  # => "localhost"

Next steps