Mobility. Typed.

This gem contains plugin for Mobility translation framework. It provides type checking for attribute writers.

Motivation

Since Mobility supports different storage backends some of them will not guarantee type safety of input data. For example Postgres (Mobility::Backend::Jsonb let us to save any kind of json-based data in single column.

class Offer < ApplicationRecord
  # ...
   
  translates :benefits
end

Offer.create!(benefits: ['fast', 'safe'])
Offer.create!(benefits: 'cheap')

Offer.find_each do |offer|
  offer.benefits.each { |benefit| Customer.notify_by_benefit(benefit) }
  # => NoMethodError (undefined method `each' for "cheap":String)
end

To prevent errors like this or at least detect them earlier we can add :type option to attribute writer configuration:

class Offer < ApplicationRecord
  # ...
   
  translates :benefits, writer: { type: :array }
end

Offer.create!(benefits: ['fast', 'safe'])
Offer.create!(benefits: 'cheap')
# => MobilityTyped::Writer::TypeError ("benefits= called with string, array expected")
# now error exposed before database records was corrupted
# so we can fix it earlier and code below will executes safely 
Offer.find_each do |offer|
  offer.benefits.each { |benefit| Customer.notify_by_benefit(benefit) }
end

Installation

Add this line to your application's Gemfile:

gem 'mobility_typed'

And then execute:

$ bundle install

Then add plugin to your mobility initializer:

# your_rails_app/config/initializers/mobility.rb
Mobility.configure do
  # ...
  plugins do
    # ...
    typed_writer
    # ...
  end
  # ...
end

And remove writer plugin from your model if you have it:

Mobility.configure do
  # ...
    plugins do
      # ...
        writer # <---- remove this line
      # ...
    end
  # ...
end

Usage

Just add type option to attribute writer configuration:

class YourModel < ApplicationRecord
  translates :your_attribute, writer: { type: :integer }
end

List of available writers types:

:string
:integer
:float
:bool
:array
:hash

Default Mobility::Plugins::Writer compatibility

To use typed_writer plugin you should remove writer plugin from your initializer. But typed_writer plugin is backward compatible with writer plugin. You can translate attributes without passing type option to writer configuration. In this case typed_writer will work just as writer plugin.

TODO:

Type checking for nested attributes, to check array and hash content
RBS generator

mobility_typed