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https://github.com/michaelherold/module_builder

Dynamically build customized Ruby modules
https://github.com/michaelherold/module_builder

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Dynamically build customized Ruby modules

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# ModuleBuilder



[![Build Status](https://travis-ci.org/michaelherold/module_builder.svg)][travis]

[![Code Climate](https://codeclimate.com/github/michaelherold/module_builder/badges/gpa.svg)][codeclimate]

[![Inline docs](http://inch-ci.org/github/michaelherold/module_builder.svg?branch=master)][inch]



[codeclimate]: https://codeclimate.com/github/michaelherold/module_builder

[inch]: http://inch-ci.org/github/michaelherold/module_builder

[travis]: https://travis-ci.org/michaelherold/module_builder



ModuleBuilder gives you the ability to create modules that are customizable for

different situations. Are you creating a module that has an adapter, but don't

want to expose a setter on the including class because it's not a public API?

ModuleBuilder can help with that! Do you have two implementations of some

behavior that have different tradeoffs? Do you want to offer both through one

easy-to-use syntax? ModuleBuilder can do that too!



Come see what ModuleBuilder will help you with today!



## Installation



Add this line to your application's Gemfile:



```ruby

gem "module_builder"

```



And then execute:



    $ bundle



Or install it yourself as:



    $ gem install module_builder



## Usage



ModuleBuilder revolves around the concept of Builders that are responsible for

building modules based on your specification. For convenience, there is a

`Buildable` module that you can mix in to give your module building

superpowers.



You configure Builders through two channels: class-level configuration and

instance-level state. There are three types of class-level configuration:

stateless inclusions, stateless extensions, and defined hooks.



Stateless methods do not give much more power than just using a standard set of

`include`s and `extend`s. However, they help you organize your code in an

easily extensible fashion.



You can use instance-level state within defined hooks to customize the behavior

of the built module. If you need to conditionally define a method based on the

configuration, you want to look here.



### Stateless Inclusions



The builder simply `include`s stateless inclusions into the built module. There

are no customization hooks here, just a single place to specify all the modules

you want to `include` in your built module.



```ruby

class StatelessInclusionBuilder < ModuleBuilder::Builder

  def inclusions

    [Comparable, Enumerable]

  end

end



StatelessInclusionBuilder.new.module.ancestors

#=> [#, Enumerable, Comparable]

```



### Stateless Extensions



The builder adds all stateless extensions into the `Module#extended` hook of

the built module so they are extended onto anything that extends the built

module.



```ruby

module Quack

  def quack

    "quack"

  end

end



class QuackingBuilder < ModuleBuilder::Builder

  def extensions

    [Quack]

  end

end



class Duck

  extend QuackingBuilder.new.module

end



Duck.quack #=> "quack"

```



### Defined Hooks



Defined hooks are where you can do the heavy customization when building a

module. They are arbitrary methods that the builder invokes during its

initialization. Add any behavior that you want to make customizable via the

state that you give to the builder as a defined hook.



```ruby

module Walk

  def walk

    "step, step, step"

  end

end



class WalkingBuilder < ModuleBuilder::Builder

  def hooks

    [:rename_walk]

  end



  def inclusions

    [Walk]

  end



  private



  def rename_walk

    return unless @walk_method



    @module.__send__(:alias_method, @walk_method, :walk)

    @module.__send__(:undef_method, :walk)

  end

end



class Duck

  include WalkingBuilder.new(:walk_method => :waddle).module

end



Duck.new.waddle  #=> "step, step, step"

Duck.new.walk    #=> NoMethodError

```



### Buildable Module



Explicitly instantiating a Builder and accessing the module that it built is

clunky. To gain easy access to a consistent syntax for your module, you can

include the `Buildable` module and specify the builder you want to use when

building your module.



```ruby

class MyBuilder < ModuleBuilder::Builder

end



module BuildableExample

  include ModuleBuilder::Buildable



  builder MyBuilder

end



module IncludingModule

  include BuildableExample.new(:state => "value")

end

```



`Buildable` defaults to using a `Builder` defined within the current module.

You can rely on that instead of using the DSL for specifying the builder.



```ruby

module OtherBuildableExample

  include ModuleBuilder::Buildable



  class Builder < ModuleBuilder::Builder

  end

end



module OtherIncludingModule

  include OtherBuildableExample.new(:my_config_value => "awesome")

end

```



When a `Buildable` module is included without the use of its constructor, the

default version of the module is included in the descendant class or module.



```ruby

module BuildableExample

  include ModuleBuilder::Buildable



  class Builder < ModuleBuilder::Builder

  end

end



module IncludingModule

  include BuildableExample

end

```



## Development



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.



When writing code, you can use the helper application [Guard][guard] to

automatically run tests and coverage tools whenever you modify and save a file.

This helps to eliminate the tedium of running tests manually and reduces the

change that you will accidentally forget to run the tests. To use Guard, run

`bundle exec guard`.



Before committing code, run `rake` to check that the code conforms to the style

guidelines of the project, that all of the tests are green (if you're writing a

feature; if you're only submitting a failing test, then it does not have to

pass!), and that the changes are sufficiently documented.



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][rubygems].



[guard]: http://guardgem.org

[rubygems]: https://rubygems.org



## Contributing



Bug reports and pull requests are welcome on GitHub at

https://github.com/michaelherold/module_builder. This project is intended to be

a safe, welcoming space for collaboration, and contributors are expected to

adhere to the [Contributor Covenant][covenant] code of conduct.



[covenant]: http://contributor-covenant.org



## Supported Ruby Versions



This library aims to support and is [tested against][travis] the following Ruby

versions:



* Ruby 1.9.3

* Ruby 2.0

* Ruby 2.1

* Ruby 2.2

* JRuby 1.7 (in Ruby 1.9 mode)

* JRuby 9.0



If something doesn't work on one of these versions, it's a bug.



This library may inadvertently work (or seem to work) on other Ruby versions,

however support will only be provided for the versions listed above.



If you would like this library to support another Ruby version or

implementation, you may volunteer to be a maintainer. Being a maintainer

entails making sure all tests run and pass on that implementation. When

something breaks on your implementation, you will be responsible for providing

patches in a timely fashion. If critical issues for a particular implementation

exist at the time of a major release, support for that Ruby version may be

dropped.



## Versioning



This library aims to adhere to [Semantic Versioning 2.0.0][semver]. Violations

of this scheme should be reported as bugs. Specifically, if a minor or patch

version is released that breaks backward compatibility, that version should be

immediately yanked and/or a new version should be immediately released that

restores compatibility. Breaking changes to the public API will only be

introduced with new major versions. As a result of this policy, you can (and

should) specify a dependency on this gem using the [Pessimistic Version

Constraint][pessimistic] with two digits of precision. For example:



    spec.add_dependency "module_builder", "~> 0.1"



[pessimistic]: http://guides.rubygems.org/patterns/#pessimistic-version-constraint

[semver]: http://semver.org/spec/v2.0.0.html



## Credits



The original implementation of this library was based on the [Builder][builder]

within the [virtus] gem by Piotr Solnica, which I used for inspiration. Pieces

of it live on, but the current product expands on the original.



The idea for the library came from [a conversation][conversation] about the

best way to configure a module once it is included in a class. [Grégory

Horion][gregory]'s comment lead me down the path of using `Module.new` as the

base for this library.



[builder]: https://github.com/solnic/virtus/blob/3248a465643b86d7fcb0c16fe6937293adbd1055/lib/virtus/builder.rb

[conversation]: https://github.com/intridea/hashie/pull/262

[gregory]: http://gregory.io

[piotr]: http://solnic.eu

[virtus]: https://github.com/solnic/virtus



## License



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



[license]: http://opensource.org/licenses/MIT.