Hatch

An address without a street? A person without a name? Those are not valid objects! Why should you have them hanging around your system?

Installation

$ gem install hatch

Usage

Tell Hatch how to certify the attributes of your models, and it will give you the appropriate object.

If you don't hatch your model with all the correct attributes, you'll get an object representing an invalid instance of it.

require 'hatch'

class Address
  include Hatch

  certify(:street, 'Address must have a street') do |street|
    !street.nil? && !street.empty?
  end

  certify(:number, 'Address must have a positive number') do |number|
    !number.nil? && number > 0
  end
end

address = Address.hatch(street: 'Fake St', number: 1234)
address.class
# => Address
address.valid?
# => true

not_an_address = Address.hatch(street: '', number: 1234)
not_an_address.class
# => Address::InvalidAddress
not_an_address.valid?
# => false

Use certify(:attribute, 'error message', &validation) to verify when an attribute is valid.

In case you're wondering, the Model::InvalidModel is polymorphic with your Model in all the reader methods declared by attr_reader or attr_accessor

Hatch also supports some common validations we all like to have! certifies(:attribute, :validation, 'error message') will do the trick.

class Address
  include Hatch

  certifies(:street, :not_empty, "This is an error! Where's my street?!")
  certifies(:number, :positive_number)
end

Common validations come in the following flavours (along with default error messages)

:not_nil - 'must not be nil'
:positive_number - 'must be a positive number'
:not_empty - 'must not be empty'

Aaand that's it for the moment. I'll keep on adding more as they come to my mind. If they come to yours first, feel free to add them and PR.

Errors

You'll also get a handy errors hash with a couple of super powers.

not_an_address = Address.hatch(street: '', number: 1234)
not_an_address.class
# => Address::InvalidAddress

not_an_address.errors.full_messages
# => ['Address must have a street']

not_an_address.errors.on(:street)
# => 'Address must have a street'

not_an_address.errors[:number]
# => []

not_an_address.errors.empty?
# => false

Interesting use cases

Hatch is essentially a validator, so you can rely on it to certify your attributes before they get to the model.

class AddressForm
  include Hatch

  certify(:street, 'Address must have a street') do |street|
    !street.nil? && !street.empty?
  end

  certify(:number, 'Address must have a positive number') do |number|
    !number.nil? && number > 0
  end
end

# Meanwhile, in your favorite Ruby web framework...
address_form = AddressForm.hatch(params['address'])

if address_form.valid?
  Address.create(params['address'])
else
  # try again
end

One of the nicest things about Hatch is that errors can be any object of your desire! Power to thy user.

class LowAwesomenessError
  attr_accessor :code, :message
end

class Address
  include Hatch

  error = LowAwesomenessError.new
  # => #<LowAwesomenessError:0x007fdb3458eeb0>
  error.code, error.message = :moar_awesome_plz, 'this is not awesome enough'

  certifies(:street, :presence, error)
end

not_an_address = Address.hatch(street: '')
not_an_address.errors.on(:street)
# => #<LowAwesomenessError:0x007fdb3458eeb0 @code=:moar_awesome_plz, @message="this is not awesome enough">

Thanks

@pote for the help, support and company!
@munshkr for testing and playing around with it.

License

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

tarolandia / hatch