transit-ruby

Transit is a data format and a set of libraries for conveying values between applications written in different languages. This library provides support for marshalling Transit data to/from Ruby.

Rationale
API docs
Specification

This implementation's major.minor version number corresponds to the version of the Transit specification it supports.

NOTE: Transit is intended primarily as a wire protocol for transferring data between applications. If storing Transit data durably, readers and writers are expected to use the same version of Transit and you are responsible for migrating/transforming/re-storing that data when and if the transit format changes.

Contributing

This library is open source, developed internally by Cognitect. We welcome discussions of potential problems and enhancement suggestions on the transit-format mailing list. Issues can be filed using GitHub issues for this project. Because transit is incorporated into products and client projects, we prefer to do development internally and are not accepting pull requests or patches.

Releases and Dependency Information

See https://rubygems.org/gems/transit-ruby

Install

gem install transit-ruby

Basic Usage

# io can be any Ruby IO

writer = Transit::Writer.new(:json, io) # or :json-verbose, :msgpack
writer.write(value)

reader = Transit::Reader.new(:json, io) # or :msgpack
reader.read

# or

reader.read {|val| do_something_with(val)}

For example:

irb(2.1.1): io = StringIO.new('', 'w+')
==========> #<StringIO:0x007faab2ec3970>
irb(2.1.1): writer = Transit::Writer.new(:json, io)
==========> #<Transit::Writer:0x007faab2e8c1c8 @marshaler=#<Transit::JsonMarshaler:0x007faab2e1a168..........(snip)..........
irb(2.1.1): writer.write("abc")
==========> nil
irb(2.1.1): writer.write(123456789012345678901234567890)
==========> nil
irb(2.1.1): io.string
==========> "[\"~#'\",\"abc\"]\n[\"~#'\",\"~n123456789012345678901234567890\"]\n"
irb(2.1.1): reader = Transit::Reader.new(:json, StringIO.new(io.string))
==========> #<Transit::Reader:0x007faab2db48e0 @reader=#<Transit::JsonUnmarshaler:0x007faab2dae030 @..........(snip)..........
irb(2.1.1): reader.read {|val| puts val}
abc
123456789012345678901234567890

Custom Handlers

Custom Write Handlers

Implement tag, rep(obj) and string_rep(obj) methods. For example:

Point = Struct.new(:x,:y) do
  def to_a; [x,y] end
end

class PointWriteHandler
  def tag(_) "point" end
  def rep(o) o.to_a  end
  def string_rep(_) nil end
end

Custom Read Handlers

Implement from_rep(rep) method. For example:

class PointReadHandler
  def from_rep(rep)
    Point.new(*rep)
  end
end

Example Usage

io = StringIO.new('', 'w+')
writer = Transit::Writer.new(:json, io,
                             :handlers => {Point => PointWriteHandler.new})
writer.write(Point.new(37,42))

p io.string.chomp
#=> "[\"~#point\",[37,42]]"

reader = Transit::Reader.new(:json, StringIO.new(io.string),
                             :handlers  => {"point" => PointReadHandler.new})
p reader.read
#=> #<struct Point x=37, y=42>

See Transit::WriteHandlers for more info.

Default Type Mapping

Transit type	Write accepts	Read returns	Example(write)	Example(read)
null	nil	nil	nil	nil
string	String	String	"abc"	"abc"
boolean	true, false	true, false	false	false
integer	Integer	Integer	123	123
decimal	Float	Float	123.456	123.456
keyword	Symbol	Symbol	:abc	:abc
symbol	Transit::Symbol	Transit::Symbol	Transit::Symbol.new("foo")	#<Transit::Symbol "foo">
big decimal	BigDecimal	BigDecimal	BigDecimal.new("2**64")	#<BigDecimal:7f9e6d33c558>
big integer	Integer	Integer	2**128	340282366920938463463374607431768211456
time	DateTime, Date, Time	DateTime	DateTime.now	#<DateTime: 2014-07-15T15:52:27+00:00 ((2456854j,57147s,23000000n),+0s,2299161j)>
uri	Addressable::URI, URI	Addressable::URI	Addressable::URI.parse("http://example.com")	#<Addressable::URI:0x3fc0e20390d4 URI:http://example.com>
uuid	Transit::UUID	Transit::UUID	Transit::UUID.new	#<Transit::UUID "defa1cce-f70b-4ddb-bb6e-b6ac817d8bc8">
char	Transit::TaggedValue	String	Transit::TaggedValue.new("c", "a")	"a"
array	Array	Array	[1, 2, 3]	[1, 2, 3]
list	Transit::TaggedValue	Array	Transit::TaggedValue.new("list", [1, 2, 3])	[1, 2, 3]
set	Set	Set	Set.new([1, 2, 3])	#<Set: {1, 2, 3}>
map	Hash	Hash	{a: 1, b: 2, c: 3}	{:a=>1, :b=>2, :c=>3}
bytes	Transit::ByteArray	Transit::ByteArray	Transit::ByteArray.new("base64")	base64
link	Transit::Link	Transit::Link	Transit::Link.new(Addressable::URI.parse("http://example.org/search"), "search")	#<Transit::Link:0x007f81c405b7f0 @values={"href"=>#<Addressable::URI:0x3fc0e202dfb8 URI:http://example.org/search>, "rel"=>"search", "name"=>nil, "render"=>nil, "prompt"=>nil}>

Additional types (not required by the transit-format spec)

Semantic type	Write accepts	Read returns	Example(write)	Example(read)
ratio	Rational	Rational	Rational(1, 3)	Rational(1, 3)

Tested Ruby Versions

• MRI 2.1.10, 2.2.7, 2.3.4, 2.4.0, 2.4.1
• JRuby 1.7.13..16

Copyright and License

Copyright © 2014 Cognitect

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.