annawinkler / domain_model

A minimal set of utilities for declaring object attributes with optional type and validation support

DomainModel

DomainModel provides a minimal set of utilties for declaring object attributes with optional type and validation support.

Usage

Add DomainModel to your class like this:

class Fish
  include DomainModel
end

Then add attributes to your class using the keyword field like this:

class Fish
  include DomainModel

  field :color, :required => true, :type => String
  field :size, :type => Float, :validate => true
  field :habitat, :type => Habitat, :validate => true
  ...

end

class Habitat
  include DomainModel

  field :temperature, :type => Float, :validate => true
  field :bottom_type, :type => String

  ...
end

The name of your field (or attribute) is required. When you specify a field, you get getters and setters automatically:

red_fish = Fish.new
red_fish.color = "red"
red_fish.habitat = Habitat.new({
  :temperature => 75.0,
  :bottom_type => "sand"
)

A field has these optional attributes:

Attribute	Description
:type	The type of the field, which could be any valid Ruby Object type, including custom classes.
:required	Is this a required field? Used for validation.
:collection	The field is an array of values. Note that you can't have a required collection.
:validate	Validate the field. If this is a collection, will validate the collection's items too.

You can extend the validation with custom code in your class:

validate :size do |errors|
  if size < 0.0 || size > 500.0 # In our world fish can only be so big
    errors.add("has to be between 0.0 and 500.0")
  end
end

Then when you create an instance of your class, you can ask if the class is valid and get any errors:

my_fish = Fish.new({ :color => "green", :size => "-10" })
if my_fish.valid?
  go_fishing
else
  my_fish.errors
end

errors is a Enumerable object of error objects. If you want to print out all of the error messages from validation, you'll want to get the flat_errors which is an array of the error messages. If you have nested DomainModel objects and you want to see all the errors, use flat_errors.

Development

To run the tests (assuming you have already run gem install bundler):

bundle install && bundle exec rake