Monads
The monads extension makes Dry::Schema::Result
objects compatible with dry-monads.
To enable the extension:
require 'dry/schema'
Dry::Schema.load_extensions(:monads)
After loading the extension, you can leverage monad API:
schema = Dry::Schema.Params { required(:name).filled(:string, size?: 2..4) }
schema.call(name: 'Jane').to_monad # => Dry::Monads::Success(#<Dry::Schema::Result{:name=>"Jane"} errors={}>)
schema.call(name: '').to_monad # => Dry::Monads::Failure(#<Dry::Schema::Result{:name=>""} errors={:name=>["must be filled"]}>)
schema.(name: "")
.to_monad
.fmap { |r| puts "passed: #{r.to_h.inspect}" }
.or { |r| puts "failed: #{r.errors.to_h.inspect}" }
This can be useful when used with dry-monads and do notation.
Using with pattern matching
Ruby 2.7 adds experimental support for pattern matching. Both dry-schema and dry-monads work with it nicely:
require 'dry/schema'
require 'dry/monads'
Dry::Schema.load_extensions(:monads)
class Example
include Dry::Monads[:result]
Schema = Dry::Schema.Params { required(:name).filled(:string, size?: 2..4) }
def call(input)
case schema.(input).to_monad
in Success(name:)
"Hello #{name}" # name is captured from result
in Failure(name:)
"#{name} is not a valid name"
end
end
end
run = Example.new
run.('name' => 'Jane') # => "Hello Jane"
run.('name' => 'Albert') # => "Albert is not a valid name"