Overview

Filterable is a micro gem that allows you to build filterable collections in a modular fashion. You can encapsulate filtering logic inside filter objects and attach them to collections.

Benefits

Reuse filtering logic between projects

For example, if you have a TimeOfDay filter, a geospatial Location filter, or an elastic search FullText filter, you can hide the horrific implementation inside a filter object.

Keep filtering logic out of your models

Keeps your models from growing out of control and taking on too much responsibility Rule #4 Extract Query Objects

Simpler to expose an API

Instead of chaining a bunch of scopes for your API response, you can instantiate a Filterable collection, pass in the get params, and present it back.

Installation

Add this line to your application's Gemfile:

gem 'filterable', github: 'coderly/filterable'

And then execute:

$ bundle

Basic Example

Imagine you have an ActiveRecord model called User with an id, username, tags, and timestamps.

class User
    acts_as_taggable
end

You could create a user collection and make use of these filters like so:

class UserCollection < Filterable::Collection
    filter :registered_after, CreatedAfterFilter
    filter :category, TagFilter
end

You could define the filters as so

 class TimeFilter
  def initialize(time)
    @time = time
  end

  def call(collection)
    if @time
        condition = collection.arel_table[:created_at].gt(@time)
        collection.where(condition)
    else
        collection
    end
  end
end

class TagFilter
  def initialize(category)
    @category = category
  end

  def call(collection)
    if @category
        collection.tagged_with @category
    else
        collection
    end
  end
end

When you then call

UserCollection.new(User.all, created_after: yesterday, category: 'moderator')

You get a collection of filtered users.