Pinball

Simple IOC Container and DI tool for ruby.

Pinball is a library for using dependency injection within Ruby applications. It provides a clear IOC Container that manages dependencies between your classes.

Features

• Stores objects, classes(as factories), blocks and singletons
• Can inject dependencies to classes and instances
• Simple DSL for configuring the container
• Stored block will be call in dependent class instance
• You can describe any context-dependent code in blocks

Usage

Class injection

Consider a Service class that has a dependency on a Repository. We would like this dependency to be available to the service when it is created.

First we create a container object and declare the dependencies.

require 'pinball'

Pinball::Container.configure do
  define :repository, Repository
end

Then we declare the repository dependency in the Service class by using the inject declaration.

class Service
  inject :repository
end

Now we can instantiate Service object and repository method will be already accessible in it's constructor! In this case repository method will return the instance of Repository. Notice: each call of repository will create new instance of Repository.

Object injection

Also you can inject any already existed object

require 'pinball'

Pinball::Container.configure do
  define :string, 'any pre-defined string'
end

In this case string method will return 'any pre-defined string'

Block injection

The most powerful feature of pinball is block injection. For example, you have FirstService class, that dependent on SecondService class, but for instantiating SecondService you need to pass @current_user from FirstService to it's constructor:

class FirstService
  inject :second_service

  def initialize(current_user)
    @current_user = current_user
  end
end

class SecondService
  def initialize(current_user)
    @current_user = current_user
  end
end

Simple defining of SecondService dependency will not work here. So we can define dependency with a block:

Pinball::Container.configure do
  define :second_service do
    SecondService.new(@current_user)
  end
end

This block will be executed it FirstService instance context where @current_user will be accessible. Notice: each call of second_service will call this block over and over again.

Singletons

Instead of class injection, singleton injection will not create new objects every time. It will create only one and then returns it. Perfect for stateless services and other singletons. Modifying of classes is not required.

Pinball::Container.configure do
  define_singleton :second_service, SingletonClass
end

class_inject

Sometimes you need to inject dependency to class, when it must be available in class methods. For this purpose Pinball has class_inject declaration:

  class Foo
    class_inject :baz
  end

  Foo.baz

Future plans

• Rails integration
• Dependency lifecycle managing in Rails context
• Smart caching

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Inspired by Encase gem