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# Rating
[](https://travis-ci.org/wbotelhos/rating)
[](https://badge.fury.io/rb/rating)
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A true Bayesian rating system with scope and cache enabled.
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## JS Rating?
This is **Raty** : https://github.com/wbotelhos/raty :star2:
## Description
Rating uses the know as "True Bayesian Estimate" inspired on [IMDb rating ](http://www.imdb.com/help/show_leaf?votestopfaq ) with the following formula:
```
(WR) = (v ÷ (v + m)) × ×
```
**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
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`R` : average for the resource
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`v` : number of votes for the resource
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`m` : average of the number of votes
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`C` : the average rating based on all resources
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## Install
Add the following code on your `Gemfile` and run `bundle install` :
```ruby
gem 'rating'
```
Run the following task to create a Rating migration:
```bash
rails g rating:install
```
Then execute the migrations to create the to create tables `rating_rates` and `rating_ratings` :
```bash
rake db:migrate
```
## Usage
Just add the callback `rating` to your model:
```ruby
class User < ApplicationRecord
rating
end
```
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Now this model can vote or receive votes.
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### rate
You can vote on some resource:
```ruby
author = User.last
resource = Article.last
author.rate(resource, 3)
```
### rating
A voted resource exposes a cached data about it state:
```ruby
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:
```ruby
author = User.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` :
```ruby
author = User.last
resource = Article.last
author.rated? resource
```
### rates
You can retrieve all rates made by some author:
```ruby
author = User.last
author.rates
```
It will return a collection of `Rate` object.
### rated
In the same way you can retrieve all rates that some author received:
```ruby
author = User.last
author.rated
```
It will return a collection of `Rate` object.
### order_by_rating
You can list resource ordered by rating data:
```ruby
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:
```ruby
Article.order_by_rating :average, :asc
```
It will return a collection of resource ordered by `Rating` table data.
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### 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.
```ruby
category_1 = Category.first
category_2 = Category.second
author = User.last
resource = Article.last
```
In this situation you should scope the vote of article with some category:
**rate**
```ruby
author.rate resource, 3, scopeable: category_1
author.rate resource, 5, scopeable: category_2
```
Now `article` has a rating for `category_1` and another one for `category_2` .
**rating**
Recovering the rating values for article, we have:
```ruby
author.rating
# nil
```
But using the scope to make the right query:
```ruby
author.rating scope: category_1
# { average: 3, estimate: 3, sum: 3, total: 1 }
author.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:
```ruby
user.rated scope: category_1
# { value: 3, scopeable: category_1 }
```
**rates**
The resource still have the power to consult its rates:
```ruby
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:
```ruby
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:
```ruby
category_1 = Category.first
category_2 = Category.second
author = User.last
resource = Article.last
author.rate resource, 1
author.rate resource, 3, scopeable: category_1
author.rate resource, 5, scopeable: 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 }
user.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 }
```
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## Love it!
Via [PayPal ](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=X8HEP2878NDEG&item_name=rating ) or [Gratipay ](https://gratipay.com/rating ). Thanks! (:
