README.md
# Criterion
[](https://rubygems.org/gems/criterion)
[](http://travis-ci.org/activefx/criterion)
[](https://codeclimate.com/github/activefx/criterion)
[](https://codeclimate.com/github/activefx/criterion/coverage)
[](https://gemnasium.com/activefx/criterion)
Criterion is a small, simple library for searching Ruby arrays and collections with a chainable, Active Record style query interface.
## Installation
Add this line to your application's Gemfile:
```ruby
gem 'criterion'
```
And then execute:
$ bundle
Or install it yourself as:
$ gem install criterion
## Usage
Consider the following example:
````ruby
require 'hashie'
require 'criterion'
matt = Hashie::Mash.new(name: 'Matt', age: 30)
mark = Hashie::Mash.new(name: 'Mark', age: 45)
john = Hashie::Mash.new(name: 'John', age: 50)
collection = [ matt, mark, john ].extend(Criterion)
````
By extending the collection with the Criterion module, you can perform chainable queries with #where, #not, #order, #limit, #offset/#skip, and calculations with #sum, #maximum, #minimum, #average.
### Where
Where is the primary method for searching a Criterion collection. All query values must match in order for a result to be returned.
Calling any query method without a value will return a Criterion::Criteria:
````ruby
collection.where
#=> #<Criterion::Criteria...
````
Searching by exact value:
````ruby
collection.where(name: 'Matt').first
#=> {"name"=>"Matt", "age"=>30}
````
Searching by regular expression:
````ruby
collection.where(name: /J/).first
#=> {"name"=>"John", "age"=>50}
````
Searching by proc:
````ruby
collection.where(age: ->(age){ age.odd? }).first
#=> {"name"=>"Mark", "age"=>45}
````
Searching by class:
````ruby
collection.where(age: Integer).all
#=> [{"name"=>"Matt", "age"=>30}, {"name"=>"Mark", "age"=>45}, {"name"=>"John", "age"=>50}]
````
Searching by range:
````ruby
collection.where(age: 42..48).all
#=> [{"name"=>"Mark", "age"=>45}]
````
Searching with multiple arguments or #where calls:
````ruby
collection.where(name: 'Matt', age: 28...32)
# is equivalent to
collection.where(name: 'Matt').where(age: 28...32)
````
All criteria must match to return a result:
````ruby
collection.where(name: 'Matt', age: 40).empty?
#=> true
````
### Or
As #where calls must match all query values, calling #or allows for an alternative query that will return results if either the #where or #or arguments match.
````ruby
collection.where(name: 'Matt').or(name: 'John').to_a
#=> [{"name"=>"Matt", "age"=>30}, {"name"=>"John", "age"=>50}]
````
For #or to work, a #where query must also be performed.
### Not
The #not method negates the query, returning matches that do not match all of the specified values. Like #where, #not can search by exact value, regular expression, class, proc, and range.
````ruby
collection.not(name: 'Matt').all
#=> [{"name"=>"Mark", "age"=>45}, {"name"=>"John", "age"=>50}]
````
All values must match for result to be excluded:
````ruby
collection.not(name: 'Matt', age: 40).empty?
#=> true
````
### Limit
Limit the number of results returned:
````ruby
collection.where(age: 0..100).limit(2).count
#=> 2
````
### Offset
Skip the specified number of records before returning a result:
````ruby
collection.where(age: 0..100).offset(1).first
#=> {"name"=>"Mark", "age"=>45}
````
### Order
Specify the field or fields with which to order the results:
````ruby
collection.order(:name).first
#=> {"name"=>"John", "age"=>50}
````
Ascending order is assumed by default, but descending can be specified:
````ruby
collection.order(age: :desc).first
#=> {"name"=>"John", "age"=>50}
````
### Calculations
A calculation method can be called end of the criteria chain to perform on operation on one of the collection's attributes.
````ruby
# Sum / total for a field:
collection.where(age: 35..55).sum(:age)
#=> 95
# Maximum value for a field:
collection.maximum(:age)
#=> 50
# Minimum value for a field:
collection.minimum(:age)
#=> 30
# Average value for a field:
collection.average(:age)
#=> 41.666666666666664
# When there are no values in the collection, nil is returned:
collection.where(age: 0..1).average(:age)
#=> nil
````
## Development
After checking out the repo, run `bin/setup` to install dependencies. Then, run `bin/console` for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release` to create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
## Contributing
1. Fork it ( https://github.com/[my-github-username]/criterion/fork )
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request