The structure is like dry-struct, except it controls optional attributes and default values aside of type constraints.
Its DSL is taken from dry-initializer. Its method attribute is just an alias for option.
require "evil-struct"
require "dry-types"
class Product < Evil::Struct
attribute :title
attribute :price, Dry::Types["coercible.float"]
attribute :quantity, Dry::Types["coercible.int"], default: proc { 0 }
# shared options
attributes optional: true do
attribute :subtitle
attribute :description
end
end
# Accepts both symbolic and string keys.
# Class methods `[]`, `call`, and `load` are just aliases for `new`
product = Product[title: "apple", "price" => "10.9", description: "a fruit"]
# Attributes are available via methods or `[]`
product.title # => "apple"
product[:price] # => 10.9
product["quantity"] # => 0
product.description # => "a fruit"
# unassigned value differs from `nil`
product.subtitle # => Dry::Initializer::UNDEFINED
# Raises in case a mandatory value was not assigned
Product.new # BOOM! because neither title, nor price are assigned
# Hashifies all attributes except for undefined subtitle
# You can use `dump` as an alias for `to_h`
product.to_h
# => { title: "apple", price: 10.9, description: "a fruit", quantity: 0 }
# The structure is comparable to any object that responds to `#to_h`
product == { title: "apple", price: 10.9, description: "a fruit", quantity: 0 }
# => true
