ReSorcery

Create resources with run-time payload type checking and link validation

Frontend clients can decode and type check JSON responses from their backends using packages like Elm's Decoders or jsonous for TypeScript.

This is a similar package for the backend, so that Ruby can perform run-time payload type checking and link validation before sending resources to the client.

A <resource> is a Hash with a :payload field (a Hash) and a :links field (an Array of <link> objects).
Each entry in the :payload is type checked using a Decoder (inspired by Elm's Decoders).
A <link> is a Hash with four fields:
- :href, which is either a URI or a String that parses as a valid URI (Addressable is used for URI-parsing, as it handles URI templates.)
- :rel, which is a white-listed String;
- :method, which is also a white-listed String; and
- :type, which is a String.

Demo:

class StaticResource
  include ReSorcery
  field :string, is(String), -> { "a string" }
  field :number, is(Numeric), -> { 42 }
  links do
    link 'self', '/here'
    link 'create', '/here', 'post'
  end
end

StaticResource.new.as_json
# {
#   :payload=>{
#     :string=>"a string",
#     :number=>42
#   }, 
#   :links=>[
#     {:rel=>"self", :href=>"/here", :method=>"get", :type=>"application/json"}, 
#     {:rel=>"create", :href=>"/here", :method=>"post", :type=>"application/json"}
#   ]
# }

Installation

Add this line to your application's Gemfile:

gem 're_sorcery'

And then execute:

$ bundle

Or install it yourself as:

$ gem install re_sorcery

Usage

class User
  include ReSorcery

  def initialize(**args)
    @args = args
  end

  def admin?
    @args[:admin] == true
  end

  field :name, String, -> { @args[:name] }
  field :id, is(Integer).and { |i| i.positive? || '`id` must be positive' }, -> { @args[:id] }
  field :admin?, is(true, false)

  links do
    link 'self', "/users/#{@args[:id]}"
    link 'destroy', "/users/#{@args[:id]}", 'delete' unless admin? # Don't delete admins
  end
end

User.new(name: "Spencer", id: 1, admin: true).as_json #=> {
#   :payload=>{:name=>"Spencer", :id=>1, :admin?=>true},
#   :links=>[
#     {:rel=>"self", :href=>"/users/1", :method=>"get", :type=>"application/json"}
#   ]
# }

# An invalid `name` raises an error when calling `as_json`
User.new(name: :Invalid, id: 1).as_json
# ReSorcery::Error::InvalidResourceError: 
#   Error at field `name` of `User`: Expected kind String, but got Symbol

The implementation of ReSorcery#as_json raises an exception on invalid data, instead of serving the error message to the user as JSON.

If you want to serve the error message to the user as JSON, use ReSorcery#resource.as_json, which will return a JSON representation of a Result object.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/spejamchr/re_sorcery.

License

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

spejamchr / re_sorcery