Korn

Korn is a data mapper from Hash to data model. Korn maps the messy HTTP forms world into nice and clean object models.

Usage

require "korn/form"

class CategoryForm < Korn::Form
  # Map a "code" property from the HTTP params into the accessor named "category_code="
  property :code, :category_code

  # Map an "id" property from the HTTP params into the accessor named "id="
  # Coerce this value to an Integer
  property :id, Integer

  # Map the "valid_on" property, coercing to a Date object when copying
  # to the model, if necessary
  property :valid_starting_on, Date

  collection :names, ->{ CategoryName.new } do
    property :id, Integer
    property :lang
    property :name
  end

  collection :synonyms, ->{ CategorySynonym.new } do
    property :id, Integer
    property :lang
    property :name, String
  end
end

# In a Rails controller
class CategoriesController < ApplicationController
  def new
    @form = CategoryForm.new
  end

  def edit
    model = Category.find(params[:id])
    @form = CategoryForm.new
    @form.copy_from(model)

    # Shortcut API
    @form = CategoryForm[Category.find(params[:id])]
  end

  def create
    @form = CategoryForm.new(params[:category])
    if @form.valid? then
      model = @form.copy_to(Category.new)
      model.save!
      render_with @form
    else
      render
    end

    # Alternatively... using the shortcut API
    @form = CategoryForm[params[:category]] do |form|
      # The form is guaranteed valid here
      form.copy_to(Category.new).save!

      # Make sure to never leave the block if you don't want to
      # generate DoubleRender errors!
      return render_with form
    end

    # else, validation failed and we need to redisplay the form
    render
  end
end

Explicitness

This library aims to be very explicit: everything is exposed; magic is reduced to an absolute minimum, and only where it makes sense (the #[] shortcut API for instantiating a form and copying values).

Installation

Add this line to your application's Gemfile:

gem 'korn'

And then execute:

$ bundle

Or install it yourself as:

$ gem install korn

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/korn. 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.

License

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