CompositeType

Composite Types for Ruby

Composite Types can be constructed to match deeper data structures:

h = { "a" => 1, "b" => :symbol }
Hash.of(String.with(Integer|Symbol)) === h  # => true

Defining types through Modules:

module Even
  def self.=== x
    Integer === x and x.even?
  end
end
Array.of(Even) === [ 2, 4, 10 ]

Composite types create dynamic Modules that redefine the #=== pattern matching operator. Thus composite types can be used in "case when" clauses:

case h
when Hash.of(String.with(Users))  ...
when Hash.of(Symbol.with(Object)) ...
end

Logical operators: #|, #&, #~ are supported:

a = [ 1, 2, 3 ]
Array.of(Positive & Integer) === a   # => true
Array.of(~ NilClass) === a           # => true

b = [ 1, -2, 3 ]
Array.of(Positive & Integer) === b   # => false

c = [ 1, 1.5, 3 ]
Array.of(Positive & Integer) === c   # => false

d = [ 1, nil, 3 ]
Array.of(~ NilClass) === d           # => false

Composite types are cached indefinitely, therefore anonymous Modules cannot be composed.

See spec/lib/composite_type_spec.rb for more examples.

Add this line to your application's Gemfile:

gem 'composite_type'

And then execute:

$ bundle

Or install it yourself as:

$ gem install composite_type

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request