Arstotzka

This project allows for a quick hash / json data fetching in order to avoid code that tries to crawl through a hash and has to constantly check for nil values or missing keys

also, this concern, like openstruct, allow the json to be manipulated as an object, but avoids method missing by aways having the declarated methods, even if that means nil return

Arstotzka is also usefull when you need keys case changed or data type cast as it was developed to be a bridge between a rails application and a Java API (Java APIs use cameCase for JSON keys)

Yard Documentation

https://www.rubydoc.info/gems/arstotzka/1.6.2

Instalation

Add Arstotzka to your Gemfile and bundle install:

Install it

  gem install arstotzka

Or add Arstotka to you Gemfile and bundle install

gem 'arstotzka'

  bundle install arstotzka

Getting Started

Include in a class that you want to wrap a json/hash

class MyParser
  include Arstotzka
end

Declare the keys you want to crawl

class MyParser
  include Arstotzka

  expose :id
  expose :name, :age, path: :person

  attr_reader :json

  def initialize(json = {})
    @json = json
  end
end

and let it fetch values from your hash

MyParser.new(
  id: 10,
  age: 22
  person: {
    name: 'Robert',
    age: 22
  }
)

this is usefull when trying to fetch data from hashes missing nodes

MyParser.new.name # returns nil

fully customise the way you crawl / fetch the information with Options
Create custom typecast

Options

after: Name of a method to be called after on the values returned
after_each: Name of a method to be called after each result
cached: Indicator that, once the value has been fetched, it should be cached (false by default)
- false : no cache
- true : simple cache where nil values are not considerated cached
- :full : full cache where even nil values are cached
case: Case of the keys from the json (lower_camel by default)
- :snake : snakecase (eg. the_key)
- :lower_camel : lower cammel case (eg. theKey)
- :upper_camel : upper cammel case (eg. TheKey)
compact: Indicator telling to ignore nil values inside array (false by default)
default: Default value (prior to casting and wrapping, see Default)
flatten: Indicator telling that to flattern the resulting array (false by default)
full_path: Full path to fetch the value (empty by default)
klass: Class to be used when wrapping the final value
json: Method that contains the hash to be parsed (:json by default)
path: Path where to find the sub hash that contains the key (empty by default)
type: Type that the value must be cast into (TypeCast)
before: method to be ran on result before any wrapping

TypeCast

The type casting, when the option type is passed, is done through the Arstotzka::TypeCast which can be extended

module Arstotzka::TypeCast
  def to_money_float(value)
    value.gsub(/\$ */, '').to_f
  end
end

class MyParser
  include Arstotzka

  expose :total_money, full_path: 'accounts.balance', after: :sum,
                       cached: true, type: :money_float
  expose :total_owed, full_path: 'loans.value', after: :sum,
                       cached: true, type: :money_float

  attr_reader :json

  def initialize(json = {})
    @json = json
  end

  private

  #this method will receive the array of values resulting from the initial mapping
  def sum(balances)
    balances.sum if balances
  end
end

object = MyParser.new(
  accounts: [
    { balance: '$ 1000.50', type: 'checking' },
    { balance: '$ 150.10', type: 'savings' },
    { balance: '$ -100.24', type: 'checking' }
  ],
  loans: [
    { value: '$ 300.50', bank: 'the_bank' },
    { value: '$ 150.10', type: 'the_other_bank' },
    { value: '$ 100.24', type: 'the_same_bank' }
  ]
)

object.total_money # returns 1050.36

Default

Default value returned before typecasting or class wrapping

class Star
  attr_reader :name

  def initialize(name:)
    @name = name
  end
end

class StarGazer
  include Arstotzka

  expose :favorite_star, full_path: 'universe.star',
         default: { name: 'Sun' }, klass: ::Star

  attr_reader :json

  def initialize(json = {})
    @json = json
  end
end

star_gazer = StarGazer.new

star_gazer.favorite_star.name # returns "Sun"

star_gazer.favorite_star.class # returns Star

Configuration

Arstotzka can be configured changing the default options

class Restaurant
  include Arstotzka

  expose :dishes, path: 'restaurant.complete_meals'

  def initialize(hash)
    @hash = hash
  end
end

hash = {
  restaurant: {
    complete_meals: {
      dishes: %w[
        Goulash
        Spaghetti
        Pizza
      ]
    }
  }
}

restaurant = Restaurant.new(hash)
restaurant.dishes # raises NoMethodError as json method is
                  # is not defined in Restaurant

Arstotzka.configure { json :@hash }

restaurant.dishes # returns nil as default case is lower_camel

Arstotzka.configure { |c| c.case :snake }

restaurant.dishes # return %s[Goulash Spaghetti Pizza]

arstotzka

Development

Runtime