Scripper

This gem allows you to strip down your Sequel model instances and hashes returned by dataset queries to simple Ruby structs.

This gem was only tested against PostgreSQL databases.

It's often convenient to simply call methods on model objects everywhere: controllers, views, serializers, business logic, and so on. But, by doing so, you're making the whole of your codebase depend on your database!

This gem is a very basic way to introduce some layer of isolation between your database and the rest of the codebase. As your application grows, it will be much simpler to transition to more mature abstractions with such isolation than without it.

The behaviour is more predictable since:

• There are no unexpected database queries (e.x. when loading associations during view rendering)
• There are no leaking database types like Sequel::Postgres::JSONBHash (these are converted to hashes automatically)

Add this line to your application's Gemfile:

gem 'scripper'

And then execute:

$ bundle

It's recommended to "wrap" this gem into a separate module:

# lib/stripper.rb

Stripper = Scripper::Sequel

It's very simple! Scripper works both with instances of Sequel::Model and hashes returned when using naked models or datasets.

# with models
user = User.first
Stripper.strip(user) # => #<struct  id=2, email="cow@cow.cow", password_hash="...">
user.email # => "cow@cow.cow"

# with datasets
user = DB[:users].first # or: User.naked.first
Stripper.strip(user) # => #<struct  id=2, email="cow@cow.cow", password_hash="...">
user.email # => "cow@cow.cow"

If you'd like to also use associations on your struct (works only with models):

user = User.first
Stripper.strip(user, with_associations: %w[cookies])
# => #<struct  id=2, ..., cookies=[#<struct  ...>, #<struct  ...>, #<struct  ...>]>

Beware that this will load all cookies associated with your user! If you want to impose some filtering conditions, you can do that:

user = User.first
Stripper.strip(
  user,
  with_associations: { cookies: -> (ds) { ds.where(active: true).limit(10) } },
)

This will only load no more than 10 active cookies.

Sometimes it's useful to provide some context beyond associations and model/dataset attributes.

In the example below, we're providing information about user's payment sum, not only user's fields.

# with a model
user = User
  .left_join(:payments)
  .select_all(:users)
  .select_append(
    Sequel.function(:sum, Sequel[:payments][:amount]).as(:payment_sum),
  )
  .group(Sequel[:users][:id])
  .first

Stripper.strip(user, with_attributes: { payment_sum: user[:payment_sum] })
# => #<struct  id=2, ..., payment_sum=418.0>

# with a dataset, it's nearly identical
user = DB[:users]
  .left_join(:payments)
  .select_all(:users)
  .select_append(
    Sequel.function(:sum, Sequel[:payments][:amount]).as(:payment_sum),
  )
  .group(Sequel[:users][:id])
  .first

Stripper.strip(user, with_attributes: { payment_sum: user[:payment_sum] })
# => #<struct  id=2, ..., payment_sum=418.0>

Sequel::Postgres::JSONHashBase (JSONBHash, JSONHash, ...) => Hash

Sequel::Postgres::JSONArrayBase (JSONBArray, JSONArray, ...) => Array

Sequel::Postgres::PGArray => Array

BigDecimal => Float

Currently, these are not extensible.

It would be lovely to:

• Make value conversions extensible
• Support ActiveRecord
• Test the gem on other databases

Your contributions and feedback are very welcome!

To run tests, you need to first create a PostgreSQL database, and then set a DB_URL variable.

Example:

DB_URL=postgres://localhost/scripper_test bundle exec rspec

If you want to enable Sequel's database access logging during spec runs, use LOG_DB=1.

Bug reports and pull requests are welcome on GitHub at https://github.com/umbrellio/scripper.

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

Created by Alexander Komarov.