Acts as Constrained

This gem includes the requried scopes and behaviours to allow to filter models using different criteria (even your own criteria).

In the end they're just a bunch of scopes and concerns so it may seem a rather uninteresting tool, but it's aimed on normalizing all the filtering behaviours and create a simple way to chain a lot of variable filters.

Install

Currently we don't have a published gem so you should use it through your Gemfile.

  gem "acts-as-constrained", git: '[email protected]:simplelogica/acts_as_constrained.git'

Usage

In order to use it you just have to add the ActsAsConstrained::Concerns::Constrained concern to your model and add constraints using the constrained_by method.

class Offer < ActiveRecord::Base

  include ActsAsConstrained::Concerns::Constrained

  constrain_by :single_date
  constrain_by :model

end

Constraints

Currently there are 3 implemented constraints: by multiple dates, a single date and another linked model.

Multiple Dates

It's implemented in the ActsAsConstrained::Concerns::DateConstraint concern.

It uses the ActsAsConstrained::DateConstraint model to store the periods of time where each object is valid and provides a scope to constrain a model according to a date.

In order to use this constrain you have to generate a migration for the required DateConstraint model. This engine provides a generator for this migration:

rails g acts_as_constrained:multiple_date_migration

Single Date

It's implemented in the ActsAsConstrained::Concerns::SingleDateConstraint concern.

It uses two attributes in the same model to perform a filter according to a date. The main difference with the MultipleDate is that you can't assign more than one period.

In order to use this constrain you have to generate a migration for those fields. This engine provides a generator for that:

rails g acts_as_constrained:single_date_migration your_model_name

Model

It allows to create a relationship between the constrained model and another one and retrieve only the records related with a constraining object.

In order to use this constrain you have to generate a migration for the required ModelConstraint model. This engine provides a generator for this migration:

rails g acts_as_constrained:model_migration

Additional constraints

You can extend this engine behaviour by creating new concerns and scopes.

The concern should follow the naming convection ActsAsConstrained::Concerns::MyConstraint replacing My with any word you like.

This concern must define a scope constrained_by_my replacing my with the underscored version of the name you gave to the concern. This scope is responsible of doing all the filtering job.

This constraint then can be included by using the constrained_by :my sentence in the model (yes, replacing my` with the underscored version of the name you gave to the concern).

Here's an example:

  module ActsAsConstrained::Concerns::CategoryConstraint

    extend ActiveSupport::Concern

    included do

      has_many :categories

      scope :constrained_by_category, ->(time = Time.now) do
        joins(:categories).where(
          categories: { published: true }
        )
      end

    end

  end

  class NewsItem < ActiveRecordBase

    include ActsAsConstrained::Concerns::Constrained

    constrain_by :category

  end

If you don't want to create a concern you can just create the constrained_by scope and not use the constrain_by sentence.

The previous code would be equivalent to

  class NewsItem < ActiveRecordBase

    include ActsAsConstrained::Concerns::Constrained

    has_many :categories

    scope :constrained_by_category, ->(time = Time.now) do
      joins(:categories).where(categories: { published: true })
    end

  end

In both cases you could do now

  NewsItem.constrained_by(category: [category1, category2])