Ishin

Ishin converts Ruby objects into their Hash representations. It works with plain old classes, extended classes, classes with mixins, and hashes (see Usage for more information).

Add this line to your application's Gemfile:

gem 'ishin'

And then execute:

bundle

Or install it manually by:

gem install ishin

Ishin does not require any other gems to run. There are a few gems used during development only, but don't affect runtime performance. For details, see ishin.gemspec in the root directory of the project.

As a class method callable on any object:

require 'ishin'

hash = Ishin.to_hash(my_object)

Or included in your object as a mixin:

class YourClass
  include Ishin::Mixin
  # etc.
end

instance = YourClass.new
hash = instance.to_hash

A simple example is worth a thousand words:

class Animal
  attr_reader :leg_count

  def initialize leg_count
    @leg_count = leg_count
  end
end

dog = Animal.new(4)

dog_hash = Ishin.to_hash(dog)
# => {:leg_count=>4}

Ishin also handles object instances nested within other object instances. By default, recursive hash conversion is turned off. To enable recursion, set the recursive option to true:

test_struct = Struct.new(:value)
nested_structs = test_struct.new(test_struct.new('value'))


Ishin.to_hash(nested_structs, recursive: true)
# => {:value=>{:value=>"value"}}

For deeply nested object instances, a maximum recursion depth can be provided in combination with the recursive option. The default recursion depth is one (initial call + 1).

nest_me = Struct.new(:value)
deep_nesting = nest_me.new(nest_me.new(nest_me.new(nest_me.new('such depth'))))

Ishin.to_hash(deep_nesting, recursive: true, recursion_depth: 2)
# => {:value=>{:value=>{:value=>#<struct value="such depth">}}}

Notice in the above example that the recursion stopped after 3 steps (initial call + 2).

Warning: Increasing the recursion depth will affect the runtime of the conversion process significantly. To see how drastic increased recursion levels affect performance, run ruby benchmarks/recursive_bench.rb

Using recursion, it is also possible to convert hashes containing object instances to a hash-only representation as well. Notice that this only works if the recursive option is provided.

another_struct = Struct.new(:value)
my_hash = {
  my_struct: another_struct.new("yup, it's a struct")
}

Ishin.to_hash(my_hash, recursive: true)
# => {:my_struct=>{:value=>"yup, it's a struct"}}

Keep in mind that the recursive option works in conjunction with the recursion_depth option.

By default, Ishin stores key names as symbols. This behavior can be disabled by setting the symbolize option to false.

class Dog
  attr_reader :says

  def initialize(says)
    @says = says
  end
end

lassie = Dog.new('Timmy is stuck in a well!')

Ishin.to_hash(lassie)
# => {:says=>"Timmy is stuck in a well!"}
Ishin.to_hash(lassie, symbolize: false)
# => {"says"=>"Timmy is stuck in a well!"}

When setting the symbolize option to false, the explicit conversion of strings to symbols is prevented. This, however, does not mean that hashes whose keys are already symbols are converted into string-based keys.

Normally, Ishin does not evaluate methods, but is possible to do so through the optional evaluate option by passing it an array of method names to evaluate.

class Speaker
  def say
    "Say what?"
  end
end

speaker = Speaker.new
# => #<Speaker:0x007fb2bb1812d8>
Ishin.to_hash(speaker, evaluate: [ :say ])
# => {:say=>"Say what?"}

It is currently only possible to evaluate methods that do not require arguments.

To use Ishin as a mixin in your own objects, simply include Ishin::Mixin:

class MyObject
  include Ishin::Mixin
  # etc.
end

Your object now exposes a method named to_hash taking the same options at the Ishin::to_hash class method documented above.

To run the code quality tools Rubocop, Reek, and RSpec, run the following command:

rake

Once bundle is executed, simply run:

rake spec

To give an idea on what kind of performance can be expected from Ishin, there are a few IPS (iterations per second) benchmarks located in the benchmarks directory. These can all be executed in series by running:

rake bench

• 0.1.0
  • Initial release.
• 0.2.0
  • Added Ishin::Mixin.
• 0.2.1
  • Now using Struct.to_h when converting a Struct instance.
• 0.3.0
  • Added support for evaluating object methods.
• 0.4.0
  • Cleanup: preparing an overhaul