NxtInit

Create an initializer that accepts option arguments and define private readers for your arguments at the same time.

Installation

Add this line to your application's Gemfile:

gem 'nxt_init'

And then execute:

$ bundle

Or install it yourself as:

$ gem install nxt_init

Usage

NxtInit removes some boilerplate. Instead of writing your initializer and (private) attribute readers each and every time like so:

class GetSafe
  def initialize(frontend:, backend:)
    @frontend = frontend
    @backend = backend
  end
  
  private 
  
  attr_reader :frontend, :backend
end

You can instead do the following:

class GetSafe
  include NxtInit
  attr_init :frontend, :backend
end

GetSafe.new # KeyError (NxtInit attr_init key :frontend was missing at initialization!
GetSafe.new(frontend: 'React', backend: 'Ruby on Rails') #<GetSafe:0x00007f81fb8506b8 @frontend="React", @backend="Ruby on Rails">

Optional arguments and defaults

In order to provide default values you can simply use the hash syntax to define your defaults. If you want to make an attribute optional, just pass nil as the default argument. If there is no default value and you did not provide one when initializing your class, you will get a KeyError.

class GetSafe
  include NxtInit
  attr_init frontend: 'React', 
            backend: -> { 'Ruby on Rails' }, 
            middleware: nil
end

GetSafe.new #<GetSafe:0x00007fab608e1918 @frontend="React", @backend="Ruby on Rails", @middleware=nil>

BEWARE of Global Defaults

class GetSafe
  include NxtInit
  attr_init frontend: [], # this is global and shared between all classes
            backend: -> { [] } # this is local to an instance of the class
end

GetSafe.new.send(:frontend).object_id => 70236117045360
GetSafe.new.send(:frontend).object_id => 70236117045360

GetSafe.new.send(:backend).object_id => 70236143937240
GetSafe.new.send(:backend).object_id => 70236121600680

Preprocessors

If you want to preprocess your attribute somehow, you can define a preprocessor block to which the original attribute will be yielded. Note that you can also call methods in your block if you have some heavier lifting to do.

class GetSafe
  include NxtInit
  attr_init date: -> (date) { date && (date.is_a?(Date) ? date : Date.parse(date)) }
end

GetSafe.new(date: '2020/12/12').send(:date) # will give you the date
GetSafe.new(date: nil).send(:date) # would give you nil
GetSafe.new # would raise KeyError (NxtInit attr_init key :date was missing at initialization!)

Also you can still pass in nil if your block can handle it. If the attribute is not provided on initialization again a KeyError will be raised.

Inheritance

When you inherit from a class that already includes NxtInit you can add further attributes to your subclass and overwrite existing options simply by using attr_init for the same attributes. Check out the specs for more examples.

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.

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/nxt-insurance/nxt_init.

License

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