ViewComposer

ViewComposer makes it easy to compose view objects for ruby apps. Create new composers, pass them a model and classes to merge, and all instance methods of the classes will be available on the composer. The Composer will also serialize these instance methods into json for an API. I like to think of it as a mix between Draper and ActiveModel Serializer but built on ideas of composition from Sandi Metz.

This is still pre-1.0 software and the API will change.

Add this line to your application's Gemfile:

gem 'view_composer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install view_composer

create a new composer that inherits from BaseComposer. and use the attributes API (similar to ActiveModel::Serializer) to let your composer know what methods to respond to.

class PostComposer < ViewComposer::BaseComposer
  attributes :id, :name, :body
end

post_composer = PostComposer.new(model: Post.new(name: "a post") )
post_composer.name #=> "a post"
post_composer.id #=> 1
post_composer.hash_attrs #=> {id: 1, name: "a post", body: nil}
post_composer.to_json #=> "{\"id\":\"1\",\"name\":\"a post\", \"body\": \"\"}"

if you would like to override the model's value you can define it as a method

class PostComposer < ViewComposer::BaseComposer
  attributes :id, :name, :body

  def name
    "special super #{@model.name}"
  end
end

post_composer.name #=> special super a post

the last part of this (that really makes it a composer) is that you can pass other classes to the composer and it will define those methods on the composer and serialize them into the same json object as well. Say you have AdminStats for your post that takes an instance of a post and responds to total_reads and referrers. ie: AdminStats.new(post).total_reads returns 1000.

your composer would look like this:

post_composer = PostComposer.new(model: post, composable_objects: [AdminStats])
post_composer.total_reads #=> 1000
post_composer.referrers #=> ["bily", "bob", "jane"]
post_composer.to_json #=> {"id": "1", "name": "a post", "body": "", "total_reads": "1000", "referrers": ["bily", "bob", "jane"] }

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.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/view_composer. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

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