rating/README.md

Rating

A true Bayesian rating system with scope and cache enabled.

JS Rating?

This is Raty: https://github.com/wbotelhos/raty 🌟

Description

Rating uses the know as "True Bayesian Estimate" inspired on IMDb rating with the following formula:

(WR) = (v ÷ (v + m)) × R + (m ÷ (v + m)) × C

IMDb Implementation:

WR: weighted rating

R: average for the movie (mean) = (Rating)

v: number of votes for the movie = (votes)

m: minimum votes required to be listed in the Top 250

C: the mean vote across the whole report

Rating Implementation:

WR: weighted rating

R: average for the resource

v: number of votes for the resource

m: average of the number of votes

C: the average rating based on all resources

Install

Add the following code on your Gemfile and run bundle install:

gem 'rating'

Run the following task to create a Rating migration:

rails g rating:install

Then execute the migrations to create the to create tables rating_rates and rating_ratings:

rake db:migrate

Usage

Just add the callback rating to your model:

class Author < ApplicationRecord
  rating
end

Now this model can vote or receive votes.

rate

You can vote on some resource:

author   = Author.last
resource = Article.last

author.rate resource, 3

rating

A voted resource exposes a cached data about it state:

resource = Article.last

resource.rating

It will return a Rating object that keeps:

average: the normal mean of votes;

estimate: the true Bayesian estimate mean value (you should use this over average);

sum: the sum of votes for this resource;

total: the total of votes for this resource.

rate_for

You can retrieve the rate of some author gave to some resource:

author   = Author.last
resource = Article.last

author.rate_for resource

It will return a Rate object that keeps:

author: the author of vote;

resource: the resource that received the vote;

value: the value of the vote.

rated?

Maybe you want just to know if some author already rated some resource and receive true or false:

author   = Author.last
resource = Article.last

author.rated? resource

rates

You can retrieve all rates received by some resource:

resource = Article.last

resource.rates

It will return a collection of Rate object.

rated

In the same way you can retrieve all rates that some author received:

author = Author.last

author.rated

It will return a collection of Rate object.

order_by_rating

You can list resource ordered by rating data:

Article.order_by_rating

It will return a collection of resource ordered by estimate desc as default. The order column and direction can be changed:

Article.order_by_rating :average, :asc

It will return a collection of resource ordered by Rating table data.

Scope

All methods support scope query, since you may want to vote on items of a resource instead the resource itself. Let's say an article belongs to one or more categories and you want to vote on some categories of this article.

category_1 = Category.first
category_2 = Category.second
author     = Author.last
resource   = Article.last

In this situation you should scope the vote of article with some category:

rate

author.rate resource, 3, scope: category_1
author.rate resource, 5, scope: category_2

Now resource has a rating for category_1 and another one for category_2.

rating

Recovering the rating values for resource, we have:

resource.rating
# nil

But using the scope to make the right query:

resource.rating scope: category_1
# { average: 3, estimate: 3, sum: 3, total: 1 }

resource.rating scope: category_2
# { average: 5, estimate: 5, sum: 5, total: 1 }

rated

On the same way you can find your rates with a scoped query:

author.rated scope: category_1
# { value: 3, scopeable: category_1 }

rates

The resource still have the power to consult its rates:

article.rates scope: category_1
# { value: 3, scopeable: category_1 }

article.rates scope: category_2
# { value: 3, scopeable: category_2 }

order_by_rating

To order the rating you do the same thing:

Article.order_by_rating scope: category_1

Records

Maybe you want to recover all records with or without scope, so you can add the suffix _records on relations:

category_1 = Category.first
category_2 = Category.second
author     = Author.last
resource   = Article.last

author.rate resource, 1
author.rate resource, 3, scope: category_1
author.rate resource, 5, scope: category_2

author.rating_records
# { average: 1, estimate: 1, scopeable: nil       , sum: 1, total: 1 },
# { average: 3, estimate: 3, scopeable: category_1, sum: 3, total: 1 },
# { average: 5, estimate: 5, scopeable: category_2, sum: 5, total: 1 }

author.rated_records
# { value: 1 }, { value: 3, scopeable: category_1 }, { value: 5, scopeable: category_2 }

article.rates_records
# { value: 1 }, { value: 3, scopeable: category_1 }, { value: 5, scopeable: category_2 }

As

If you have a model that will only be able to rate but not to receive a rate, configure it as author. An author model still can be rated, but won't genarate a Rating record with all values as zero to warm up the cache.

rating as: :author

Metadata

Maybe you want include a comment together your rating or even a fingerprint field to make your rating more secure. So, first you will need to add more fields to the Rating::Rate table:

class AddCommentAndFingerprintOnRatingRates < ActiveRecord::Migration
  def change
    add_column :rating_rates, :comment, :text

    add_reference :rating_rates, :fingerprint, foreign_key: true, index: true, null: false
  end
end

As you can seed, we can add any kind of field we want. Now we just provide this values when we make the rate:

author      = Author.last
resource    = Article.last
comment     = 'This is a very nice rating. s2'
fingerprint = Fingerprint.new(ip: '127.0.0.1')

author.rate resource, 3, metadata: { comment: comment, fingerprint: fingerprint }

Now you can have this data into your model normally:

author = Author.last
rate   = author.rates.last

rate.comment     # 'This is a very nice rating. s2'
rate.fingerprint # <Fingerprint id:...>
rate.value       # 3

Scoping

If you need to warm up a record with scope, you need to setup the scoping relation.

class Resource < ApplicationRecord
  voting scoping: :categories
end

Now, when a resource is created, the cache will be generated for each related category as scopeable.

Table Name

You can choose the table where Rating will write the data via YAML config. You should just to provide a config/rating.yml file with the following content:

rating:
  rate_table: 'reviews'
  rating_table: 'review_ratings'

Now the rates will be written on reviews table over rating_rates and calculation will be on review_ratings over rating_ratings. You can change one table o both of them.

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