QHash - ActiveRecord style query interface for Hash

QHash lets you query array of hashes with ActiveRecord-like interface.

What's the point?

We often do something like

users.select do |user|
  (dob = user.dig(:personal_data, :date_of_birth)) &&
    dob > Date.new(1990, 1, 1) &&
    user.dig(:address, :country) == "Germany" &&
    user.dig(:address, :city) == "Hamburg"
end

which can quickly become hard to read.

QHash provides syntax sugar that would allow you to do

users.where(
  personal_data: {
    date_of_birth: ->(dob) { dob > Date.new(1990, 1, 1) }
  },
  address: {country: "Germany", city: "Hamburg"}
)

Installation

Add this line to your application's Gemfile:

gem 'q_hash'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install q_hash

Usage

Let's say you have the following array of hash:

data = [
  {
    id: "da9d517e-eb1b-4f5b-8fec-c1258eda0db2",
    personal_info: {
      name: "John Doe",
      date_of_birth: "1900-01-01"
    },
    address: {
      country: "Japan",
      city: "Tokyo"
    },
    hobbies: [
      "jogging",
      "eating",
      "sleeping"
    ]
  },
  {
    id: "fab15d98-47d6-4552-a6e6-0b83de0b532b",
    personal_info: {
      name: "John Doe Jr.",
      date_of_birth: "2000-01-01"
    },
    address: {
      country: "Japan",
      city: "Tokyo"
    },
    biometrics: {
      height: 200,
      weight: 100
    }
  }
]

QHash#find_by

QHash.new(data).find_by(id: "fab15d98-47d6-4552-a6e6-0b83de0b532b")
# =>
#   {:id=>"fab15d98-47d6-4552-a6e6-0b83de0b532b",
#     :personal_info=>{:name=>"John Doe Jr.", :date_of_birth=>"2000-01-01"},
#     :address=>{:country=>"Japan", :city=>"Tokyo"},
#     :biometrics=>{:height=>200, :weight=>100}}

Note that #find_by returns the first record that matches the condition, just like Array#find_by.

There's also QHash#find_by!, which raises QHash::RecordNotFound in case there's no record to be found.

QHash#where

QHash.new(data).where(personal_info: { name: 'John Doe' })
# => [{:id=>"da9d517e-eb1b-4f5b-8fec-c1258eda0db2", :personal_info=>{:name=>"John Doe", :date_of_birth=>"1900-01-01"}, :address=>{:country=>"Japan", :city=>"Tokyo"}, :hobbies=>["jogging", "eating", "sleeping"]}]

Note that #where returns an instance of QHash, not an array of hashes. But no worries, QHash is also an Enumerable.

Proc condition

If you'd like to query by more complex conditions, you can also use Procs

QHash.new(data).where(biometrics: {height: ->(height) { height > 100 }})
# => [{:id=>"fab15d98-47d6-4552-a6e6-0b83de0b532b", :personal_info=>{:name=>"John Doe Jr.", :date_of_birth=>"2000-01-01"}, :address=>{:country=>"Japan", :city=>"Tokyo"}, :biometrics=>{:height=>200, :weight=>100}}]

Chaining #where and #find_by

You can also chain #where and #find_by:

QHash.new(data)
      .where(address: {country: "Japan", city: ["Tokyo", "Osaka"]})
      .where(biometrics: {height: ->(height) { height > 100 }})
      .find_by(id: data.last[:id])
# =>
#   {:id=>"fab15d98-47d6-4552-a6e6-0b83de0b532b",
#     :personal_info=>{:name=>"John Doe Jr.", :date_of_birth=>"2000-01-01"},
#     :address=>{:country=>"Japan", :city=>"Tokyo"},
#     :biometrics=>{:height=>200, :weight=>100}}

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also 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, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/AkihikoITOH/q_hash. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the QHash project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.