FieldStruct AvroSchema

FieldStruct provides a lightweight approach to having typed structs in three flavors: Flexible, Strict and Mutable.

This gem provides support for Avro schemas for FieldStruct classes.

Usage

Say you have a user class like this:

require 'field_struct'
require 'field_struct/avro_schema'

class Friend < FieldStruct.strict
  include FieldStruct::AvroExtension
  
  required :name, :string
  optional :age, :integer
  optional :balance_owed, :currency, default: 0.0
  optional :gamer_level, :integer, enum: [1,2,3], default: -> { 1 }  
  optional :zip_code, :string, format: /\A[0-9]{5}?\z/  
end

puts Friend.metadata.as_avro_schema.inspect
# {:type=>"record",
#  :name=>"friend",
#  :doc=>"| version 82f78509",
#  :fields=>
#    [{:name=>"name", :type=>"string", :doc=>"| type string"},
#     {:name=>"age", :type=>["null", "int"], :default=>nil, :doc=>"| type integer"},
#     {:name=>"balance_owed", :type=>["null", "float"], :default=>nil, :doc=>"| type currency"},
#     {:name=>"gamer_level", :type=>["null", "int"], :default=>nil, :doc=>"| type integer"},
#     {:name=>"zip_code", :type=>["null", "string"], :default=>nil, :doc=>"| type string"}]}

puts Friend.metadata.to_avro_json true
# {
#   "type": "record",
#   "name": "friend",
#   "doc": "| version 82f78509",
#   "fields": [
#     {
#       "name": "name",
#       "type": "string",
#       "doc": "| type string"
#     },
#     {
#       "name": "age",
#       "type": [
#         "null",
#         "int"
#       ],
#       "default": null,
#       "doc": "| type integer"
#     },
#     {
#       "name": "balance_owed",
#       "type": [
#         "null",
#         "float"
#       ],
#       "default": null,
#       "doc": "| type currency"
#     },
#     {
#       "name": "gamer_level",
#       "type": [
#         "null",
#         "int"
#       ],
#       "default": null,
#       "doc": "| type integer"
#     },
#     {
#       "name": "zip_code",
#       "type": [
#         "null",
#         "string"
#       ],
#       "default": null,
#       "doc": "| type string"
#     }
#   ]
# }

We can also generate a new FieldStruct metadata from the Avro definition we just generated. And with that we can generate a new FieldStruct class.

meta = FieldStruct::Metadata.from_avro_schema Friend.metadata.as_avro_schema
# => [#<FieldStruct::Metadata name="Schemas::Friend::V82f78509" version="82f78509" type=:flexible>]
FieldStruct.from_metadata meta.last
# => Schemas::Friend::V82f78509

And with that new class we can create new instances:

john = Schemas::Friend::V82f78509.new age: 18
# => #<Schemas::Friend::V82f78509 age=18>  
john.valid?
# => false
john.errors.messages
# => {:name=>["can't be blank"]}
john = Schemas::Friend::V82f78509.new name: 'John', age: 18
# => #<Schemas::Friend::V82f78509 name="John" age=18>
john.valid?
# => true 

Installation

Add this line to your application's Gemfile:

gem 'field_struct_avro_schema'

And then execute:

$ bundle

Or install it yourself as:

$ gem install field_struct_avro_schema

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Publishing

0. Ensure you are configured for publishing. See this
1. Build the gem gem build field_struct_avro_schema.gemspec
2. Publish the gem gem push --key github --host https://rubygems.pkg.github.com/acima-credit field_struct_avro_schema-x.x.x.gem

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/acima-credit/field_struct.

License

The gem is available as open source under the terms of the MIT License.