Monads
The monads extension makes Dry::Types::Result objects compatible with dry-monads.
To enable the extension:
require 'dry/types'
Dry::Types.load_extensions(:monads)
After loading the extension, you can leverage monad API:
Types = Dry.Types()
result = Types::String.try('Jane')
result.class #=> Dry::Types::Result::Success
monad = result.to_monad
monad.class #=> Dry::Monads::Result::Success
monad.value! # => 'Jane'
result = Types::String.try(nil)
result.class #=> Dry::Types::Result::Failure
monad = result.to_monad
monad.class #=> Dry::Monads::Result::Failure
monad.failure # => [#<Dry::Types::ConstraintError>, nil]
Types::String.try(nil)
.to_monad
.fmap { |result| puts "passed: #{result.inspect}" }
.or { |error, input| puts "input '#{input.inspect}' failed with error: #{error.to_s}" }
This can be useful when used with dry-monads and the do notation:
require 'dry/types'
Types = Dry.Types()
Dry::Types.load_extensions(:monads)
class AddTen
include Dry::Monads[:result, :do]
def call(input)
integer = yield Types::Coercible::Integer.try(input)
Success(integer + 10)
end
end
add_ten = AddTen.new
add_ten.call(10)
# => Success(20)
add_ten.call('integer')
# => Failure([#<Dry::Types::CoercionError: invalid value for Integer(): "integer">, "integer"])