Module: ObjectForge::Molds

Defined in:

lib/object_forge/molds.rb,
lib/object_forge/molds/hash_mold.rb,
lib/object_forge/molds/mold_mold.rb,
lib/object_forge/molds/struct_mold.rb,
lib/object_forge/molds/wrapped_mold.rb,
lib/object_forge/molds/keywords_mold.rb,
lib/object_forge/molds/single_argument_mold.rb

Overview

This module provides a collection of predefined molds to be used in common cases.

Molds are #callable objects responsible for actually building objects produced by factories (or doing other, interesting things with them (truly, only the code review is the limit!)). They are supposed to be immutable, shareable, and persistent: initialize once, use for the whole runtime.

A simple mold can easily be just a Proc. All molds must have the following #call signature: call(forged:, attributes:, **). The extra keywords are for future extensions.

Examples:

A very basic FactoryBot replacement

creator = ->(forged:, attributes:, **) do
  instance = forged.new
  attributes.each_pair { instance.public_send(:"#{_1}=", _2) }
  instance.save!
end
creator.call(forged: User, attributes: { name: "John", age: 30 })
  # => <User name="John" age=30>

Using a mold to serialize collection of objects (contrivedly)

dumpy = ->(forged:, attributes:, **) do
  Enumerator.new(attributes.size) do |y|
    attributes.each_pair { y << forged.dump(_1 => _2) }
  end
end
dumpy.call(forged: JSON, attributes: {a:1, b:2}).to_a
  # => ["{\"a\":1}", "{\"b\":2}"]
dumpy.call(forged: YAML, attributes: {a:1, b:2}).to_a
  # => ["---\n:a: 1\n", "---\n:b: 2\n"]

Abstract factory pattern (kind of)

class FurnitureFactory
  def call(forged:, attributes:, **)
    concrete_factory = concrete_factory(forged)
    attributes[:pieces].map do |piece|
      concrete_factory.public_send(piece, attributes.dig(:color, piece))
    end
  end
  private def concrete_factory(style)
    case style
    when :hitech
      HiTechFactory.new
    when :retro
      RetroFactory.new
    end
  end
end
FurnitureFactory.new.call(forged: :hitech, attributes: {
  pieces: [:chair, :table], color: { chair: :black, table: :white }
})
  # => [<#HiTech::Chair color=:black>, <#HiTech::Table color=:white>]

Abusing molds

printer = ->(forged:, attributes:, **) { PP.pp(attributes, forged) }
printer.call(forged: $stderr, attributes: {a:1, b:2})
  # outputs "{:a=>1, :b=>2}" to $stderr

Since:

• 0.2.0

Defined Under Namespace

Classes: HashMold, KeywordsMold, MoldMold, SingleArgumentMold, StructMold, WrappedMold