protobuf/ruby/README.md

This directory contains the Ruby extension that implements Protocol Buffers
functionality in Ruby.

The Ruby extension makes use of generated Ruby code that defines message and
enum types in a Ruby DSL. You may write definitions in this DSL directly, but we
recommend using protoc's Ruby generation support with .proto files. The build
process in this directory only installs the extension; you need to install
protoc as well to have Ruby code generation functionality. You can build protoc
from source using `bazel build //:protoc`.

Installation from Gem
---------------------
In Gemfile (Please check which version of Protocol Buffers you need: [RubyGems](https://rubygems.org/gems/google-protobuf)):

    gem 'google-protobuf'

Or for using this pre-packaged gem, simply install it as you would any other gem:

    $ gem install [--prerelease] google-protobuf

Once the gem is installed, you may or may not need `protoc`. If you write your
message type descriptions directly in the Ruby DSL, you do not need it.
However, if you wish to generate the Ruby DSL from a `.proto` file, you will
also want to install Protocol Buffers itself, as described in this repository's
main `README` file. The version of `protoc` included in the latest release
supports the `--ruby_out` option to generate Ruby code.

A simple example of using the Ruby extension follows. More extensive
documentation may be found in the RubyDoc comments (`call-seq` tags) in the
source, and we plan to release separate, more detailed, documentation at a
later date.

```ruby
require 'google/protobuf'

# generated from my_proto_types.proto with protoc:
#  $ protoc --ruby_out=. my_proto_types.proto
require 'my_proto_types'

mymessage = MyTestMessage.new(:field1 => 42, :field2 => ["a", "b", "c"])
mymessage.field1 = 43
mymessage.field2.push("d")
mymessage.field3 = SubMessage.new(:foo => 100)

encoded_data = MyTestMessage.encode(mymessage)
decoded = MyTestMessage.decode(encoded_data)
assert_equal mymessage, decoded
puts "JSON:"
puts MyTestMessage.encode_json(mymessage)
```

Installation from Source (Building Gem)
---------------------------------------
 

Protocol Buffers has a new experimental backend that uses the
[ffi](https://github.com/ffi/ffi) gem to provide a unified C-based
implementation across Ruby interpreters based on
[UPB](https://github.com/protocolbuffers/upb). For now, use of the FFI
implementation is opt-in. If any of the following are true, the traditional
platform-native implementations (MRI-ruby based on CRuby, Java based on JRuby)
are used instead of the new FFI-based implementation: 1. `ffi` and
`ffi-compiler` gems are not installed 2. `PROTOCOL_BUFFERS_RUBY_IMPLEMENTATION`
environment variable has a value other than `FFI` (case-insensitive). 3. FFI is
unable to load the native library at runtime.

To build this Ruby extension, you will need:

* Rake
* Bundler
* Ruby development headers
* a C compiler

To Build the JRuby extension, you will need:

* Maven
* The latest version of the protobuf java library (see ../java/README.md)
* Install JRuby via rbenv or RVM

First switch to the desired platform with rbenv or RVM.

Then install the required Ruby gems:

    $ gem install bundler
    $ bundle

Then build the Gem:

    $ rake
    $ rake clobber_package gem
    $ gem install `ls pkg/google-protobuf-*.gem`

To run the specs:

    $ rake test

To run the specs while using the FFI-based implementation:

```
$ PROTOCOL_BUFFERS_RUBY_IMPLEMENTATION=FFI rake test
```

This gem includes the upb parsing and serialization library as a single-file
amalgamation. It is up-to-date with upb git commit
`535bc2fe2f2b467f59347ffc9449e11e47791257`.

Alternatively, you can use Bazel to build and to run tests.

From the project root (rather than the `ruby` directory):

```
$ bazel test //ruby/tests/...
```

To run tests against the FFI implementation:

```
$ bazel test //ruby/tests/... //ruby:ffi=enabled --test_env=PROTOCOL_BUFFERS_RUBY_IMPLEMENTATION=FFI
```

Version Number Scheme
---------------------

We are using a version number scheme that is a hybrid of Protocol Buffers'
overall version number and some Ruby-specific rules. Gem does not allow
re-uploads of a gem with the same version number, so we add a sequence number
("upload version") to the version. We also format alphabetical tags (alpha,
pre, ...) slightly differently, and we avoid hyphens. In more detail:

* First, we determine the prefix: a Protocol Buffers version "3.0.0-alpha-2"
  becomes "3.0.0.alpha.2". When we release 3.0.0, this prefix will be simply
  "3.0.0".
* We then append the upload version: "3.0.0.alpha.2.0" or "3.0.0.0". If we need
  to upload a new version of the gem to fix an issue, the version becomes
  "3.0.0.alpha.2.1" or "3.0.0.1".
* If we are working on a prerelease version, we append a prerelease tag:
  "3.0.0.alpha.3.0.pre". The prerelease tag comes at the end so that when
  version numbers are sorted, any prerelease builds are ordered between the
  prior version and current version.

These rules are designed to work with the sorting rules for
[Gem::Version](http://ruby-doc.org/stdlib-2.0/libdoc/rubygems/rdoc/Gem/Version.html):
release numbers should sort in actual release order.