Canister

Summary

Canister is a simple IoC container for ruby. It has no dependencies and provides only the functionality you need. It does not monkey-patch ruby or pollute the global namespace, and most importantly it expects to be invisible to your domain classes.

It provides:

• Out-of-order declaration
• Caching
• Automatic dependency resolution
• Automatic cache invalidation on re-registration

Why do I need this? Especially in ruby?

Canister was created to make it easier to declare our setup for our application's production and test environments in a single place, without needing to know when exactly those objects were created.

Canister is not a replacement for dependency injection. Rather, it is useful when you have designed your objects to have their dependencies injected. For example, it would be a mistake to write all of your classes such that they except a single parameter called container.

For more information on dependency injection and inversion of control containers in ruby, please see this excellent article by Blair Anderson that both sums up the issue and was the inspiration for this gem.

Installation

Add it to your Gemfile and you're off to the races.

Usage

# Basic usage
container = Canister.new
container.register(:foo) { "foo" }
container.register(:bar) {|c| c.foo + "bar" }

container.bar     #=> "foobar"
container[:bar]   #=> "foobar"
container["bar"]  #=> "foobar"

# Dependencies can be declared in any order
container.register(:after) {|c| "#{c.before} and after" }
container.register(:before) { "before" }
container.after   #=> "before and after"

# Values are cached
container.register(:wait) { sleep 3; 27 }
container.wait
  .
  .
  .
  #=================> 27
container.wait    #=> 27

# Caches are invalidated automatically
container.register(:foo) { "oof" }
container.bar     #=> "oofbar"

Contributing

Standard rules apply.

Compatibility

• ruby 2.3.x
• ruby 2.4.x

As Canister does not rely on any specific runtime environment other than the ruby core, it is compatible with every ruby library and framework.

Authors

• The author and maintainer is Bryan Hockey
• This project was inspired by this excellent article by Blair Anderson. (We are not affiliated, so don't blame him if this breaks.)

License

Copyright (c) 2018 The Regents of the University of Michigan.
All Rights Reserved.
Licensed according to the terms of the Revised BSD License.
See LICENSE.md for details.