Comandante/Msgpack

An add-on for Comandante for simplifying msgpack reading/writing.

Installation

1. Add the dependency to your shard.yml:

dependencies:
  comandante-msgpack:
    github: tghaleb/comandante-msgpack

1. Run shards install

Usage

require "comandante-msgpack"

This is actually a wrapper around msgpack-crsytal. By default Crystal types will be serializable, but for custom classes to be serializable you need to add something like this to your class.

require "msgpack"

class Location
  include MessagePack::Serializable

  property lat : Float64
  property lng : Float64
end

You can either use the reader to write a large object to a file,

Helper.write_msgpack(my_object, file)

Or use in an append mode and append multiple objects, of the same type, to file.

objects.each do |x|
  Helper.write_msgpack(x, file, mode: "a")
end

If you need something more complicated than this use msgpack-crsytal directly.

To read one object,

data = Helper.read_msgpack(f, Array(Int32).new)

This will raise an error if you pass the wrong data type or in case the file is empty.

To read multiple objects, for example multiple Arrays from a file,

Helper.read_msgpack(f, Array(Float64).new) do |data|
  puts data.inspect
end