Strong Arms

A nested parameters friendly alternative to strong_parameters found in Rails.

Strong Arms provides a simple whitelisting interface and tells you when it encounters unexpected params.

Add this line to your application's Gemfile:

gem 'strong_arms'

And then execute:

$ bundle

Or install it yourself as:

$ gem install strong_arms

Controller Definition

class PostController < ApplicationController
  def create
    post = Post.create(post_params)
    render json: post
  end

  def update
    post = Post.find(params[:id])
    post.update(post_params)
    render json: post
  end

  private

  def post_params
    PostStrongArm.flex(params[:post])
  end
end

Strong Arms Definition

# app/strong_arms

class PostStrongArm
  extend StrongArms

  ignore :created_at, :updated_at

  permit :id
  permit :title
  permit :description
  permit :user_id, required: true

  many_nested :comments
end

class CommentStrongArm
  extend StrongArms

  ignore :created_at, :updated_at

  permit :id
  permit :body
  permit :user_id, required: true
end

Permitted parameters are defined in Strong Arms with the permit method.

If parameters are passed to Strong Arms without being permitted, Strong Arms will raise an exception.

class UserStrongArm
  extend StrongArms

  permit :id
end

Permitted parameters can be "required", by passing the :required option.

When required, Strong Arms expects parameter data to be present.

If it is absent, Strong Arms will raise an exception.

class UserStrongArm
  extend StrongArms

  permit :id
  permit :email, required: true
end

Parameters passed to Strong Arms can be ignored, with the ignore method.

Commonly ignored parameters include auto incremented or optional (nillable) values.

class UserStrongArm
  extend StrongArms

  ignore :created_at, :updated_at

  permit :id
  permit :email, required: true
end

Strong Arms handles nested parameters, by specifying a relationship with many_nested or one_nested methods.

This is similar to how Rails handles association declarations with has_many and has_one methods.

class UserStrongArm
  extend StrongArms

  ignore :created_at, :updated_at

  permit :id
  permit :email, required: true

  many_nested :posts # has_many :posts
  one_nested :profile # has_one :profile
end

class PostStrongArm
  extend StrongArms

  ignore :created_at, :updated_at

  permit :id
  permit :title
  permit :user_id, required: true
end

class ProfileStrongArm
  extend StrongArms

  ignore :created_at, :updated_at

  permit :id
  permit :name
  permit :birthday
  permit :user_id, required: true
end

Strong Arms expects nested parameters to follow the accepts_nested_attributes_for convention.

  many_nested :posts # { posts_attributes: [] }
  one_nested :profile # { profile_attributes: {} }

If you do not wish to use accepts_nested_attributes_for, provide the :format option.

  many_nested :posts, format: false # { posts: [] }
  one_nested :profile, format: false # { profile: {} }

If Strong Arms cannot find the relevant Strong Arms class for the nested resource, it will raise an exception.

Sometimes failure to find the relevant Strong Arm occurs due to irregular plural conjugations.

You can pass the appropriate model name via the :model option:

  many_nested :loaves, model: :loaf
  one_nested :address, model: :address

This also comes in handy for plural words ending in es, or if you'd like to match the key to an alias Strong Arm.

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/launchpadlab/strong_arms. 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.

Everyone interacting in the Strong Arms project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.