Dinja

Dinja, Dependency Injection Ninja

Installation

Add this line to your application's Gemfile:

gem "dinja"

And then execute:

$ bundle install

Or install it yourself as:

$ gem install dinja

Usage

Standalone

# Instantiate a dependency injection container
container = Dinja::Container.new

# Register a dependency
container.register("my_dependency") { |name| OpenStruct.new(name: name) }

# Resolve a dependency
my_dependency = container.resolve("my_dependency", "foobar")

puts my_dependency.name
# => "foobar"

# Look up a dependency (without resolving)
my_dependency = container.lookup("my_dependency")
puts my_dependency.call("foobar")
# => #<OpenStruct name="foobar">

# Container#resolve will raise when trying to resolve unregistered dependencies
# Use Container#resolve! to resolve unregistered dependencies without raising (dangerous)
container.resolve("another_dependency")
# => DependencyNotRegistered

# Container#lookup will raise when trying to look up unregistered dependencies
# Use Container#lookup! to look up unregistered dependencies without raising (dangerous)
container.lookup("another_dependency")
# => DependencyNotRegistered

# Container#register will raise when trying to overwrite registered dependencies
# Use Container#register! to overwrite dependencies (dangerous)
container.register("my_dependency") { |name| OpenStruct.new(name: name) }

Rails

In a Rails application, add the following line to your config/application.rb:

require "dinja/railtie"

Create config/dependencies.rb and register some dependencies:

register("my_dependency") do |name|
  OpenStruct.new(name: name)
end

A dependency injection container is now available throughout your application on Rails.application.config.container:

my_dependency = Rails.application.config.container.resolve("my_dependency", "foobar")

my_dependency.name
# => "foobar"

Gem

In a gem, add the following lines to your lib/my_gem.rb:

require "dinja"

module MyGem
  def container
    @container ||= Dinja::Container.new 
  end

  def setup
    # ...other stuff here

    # Register dependencies
    container.instance_eval(File.read("config/dependencies.rb"))
  end
end

MyGem.setup

Create config/dependencies.rb and register some dependencies:

register("my_dependency") do |name|
  OpenStruct.new(name: name)
end

A dependency injection container is now available throughout your application on MyGem.container:

my_dependency = MyGem.container.resolve("my_dependency", "foobar")

my_dependency.name
# => "foobar"

RSpec

If you need to mock resolution calls to a container, you can do as following.

In spec/rails_helper.rb or spec/spec_helper.rb:

require "dinja/rspec"
include Dinja::RSpec

In config/dependencies.rb:

register("my_service") do |name|
  OpenStruct.new(name: name)
end

In spec/my_app/my_model_spec.rb:

RSpec.describe MyApp::MyModel do
  subject(:my_model) { described_class.new }

  it "calls my service" do
    my_service = dinja_mock!("my_service")

    allow(my_service)
      .to receive(:call)
      .and_return true

    my_model.call_service

    expect(my_service).to have_received(:call)
  end
end

Development

To release a new version, update the version number in lib/dinja/version.rb, update the changelog, commit the files and create a git tag starting with v, and push it to the repository. Github Actions will automatically run the test suite, build the .gem file and push it to rubygems.org.

Contributing

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

License

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