Exprotoc

Elixir protocol buffers compiler

Mix project options

To use exprotoc, first include exprotoc in your mixfile as a dependency. Then, in the project property of your mix project, add :exprotoc to the list of compilers (e.g. compilers: [:exprotoc, :elixir, :app).

To configure the :exprotoc compiler prepass, there are three exposed options: proto_out, proto_files, and proto_path.

proto_out

Binary string that represents the directory generated code should be output to. Defaults to the lib folder.

proto_files

This should be a list of all the proto files you wish to turn into elixir code.

proto_path

List of directories in the order exprotoc should visit to look for proto files and imports.

Example mix.exs file

defmodule Example.Mixfile do
  use Mix.Project

  def project do
    [ app: :example,
      version: "0.0.1",
      elixir: "~> 0.12.5",
      compilers: [:exprotoc, :elixir, :app],
      proto_files: ["example.proto"],
      proto_path: ["priv"],
      deps: deps ]
  end

  defp deps do
    [{ :exprotoc, github: "jeremyong/exprotoc" }]
  end
end

This will compile the Example application with the generated code for the proto file example.proto. Because no proto_out option is specified, the generated code will be output to the lib folder.

Usage

Just access your message modules as you would a standard Elixir dict.

For example, with the following proto message:

package Example;
message Foo {
  enum Bar {
    Zap = 150;
  }
  required Foo a = 1;
  required uint32 b = 2;
}

exprotoc will create a module Example.Foo and submodule Example.Foo.Bar.

You can create a new message simply with Example.Foo.new or Example.Foo.new a: Example.Foo.Bar.zap.

You can access your message with the access protocol. For example:

message = Example.Foo.new a: Example.Foo.Bar.zap
IO.inspect message[:a] # Will output { Example.Foo.Bar, :zap }
IO.inspect message[:b] # Will output nil
message = Example.Foo.put message, :b, 150
IO.inspect message[:b] # Will output 150

All message modules export the encode and decode functions to turn a message into an iolist or turn binary into a message.

Default values work as expected.

Repeated fields are represented as lists.