Literal properties

Literal::Properties is a module that you can extend into any class hierarchy to add property macros.

Properties can be defined like this:

class Person
  extend Literal::Properties

  prop :name, String
  prop :age, Integer
end

The first argument to prop is the name of the property, and the second argument is the type. Person now has an initializer that takes name: and age: keyword arguments and assigns them to the instance variables @name and @age.

Different kinds of arguments

You can also define properties that take different kinds of arguments.

Positional argument:

prop :name, String, :positional

Positional *rest:

prop :names, _Array(String), :*

Keyword **rest:

prop :options, _Hash(Symbol, String), :**

Blocks:

prop :block, Proc, :&

Type coercion

You can optionally pass a block to prop that will be used to coerce the value to the correct type.

prop :age, Integer do |value|
  value.to_i
end

The value will pass through the block before being type-checked or assigned to the instance variable.

Optional properties

All properties are required unless the type is nilable.

prop :name, _Nilable(String)

Since the type _Nilable(String) can be nil, the property is optional.

Attribute accessors

You can also specify that Literal should generate attribute readers/writers for properties.

prop :name, String, reader: :public, writer: :protected

Default values

Properties can have defaults that are either Procs or frozen objects.

prop :first_name, String, default: -> { "John" }
prop :last_name, String, default: "Doe".freeze