Mixture

Add this line to your application's Gemfile:

gem 'mixture'

And then execute:

$ bundle

It's simple, really.

module MyLibrary
  class MyClass
    include Mixture::Model
  end
end

This provides a few simple things. First off, it provides the .attribute class method. The attribute class method allows you to define an attribute on your class. Attributes use the instance variables just like attr_reader/attr_writer do - but it also allows coercion on assignment, as well. Defining an attribute is as simple as attribute :name. This provides the :name and :name= methods on the instance.

You also get access to the #attributes=, #attributes, and #attribute instance methods. The first group assigns attributes, running it through any update callbacks defined. The second retrieves the attributes on the instance, even if they weren't assigned. The last provides easy get/set functionality.

If you want to take advantage of the coercion abilities, just add a :type key to the options for the attribute:

module MyLibrary
  class MyClass
    include Mixture::Model

    attribute :name, type: String
  end
end

This will automagically cause name to be coerced to a string on assignment.

For validation, use the .validate class method:

module MyLibrary
  class MyClass
    include Mixture::Model
    attribute :name, type: String
    validate :name, format: /^.{3,20}$/
  end
end

Some validators are available by default:

• :exclusion - Validates that the value for the attribute is not within a given set of values.
• :inclusion - Validates that the value for the attribute is within a given set of values.
• :length - Validates that the value for the attribute is within a certain length.
• :match - Validates that the value for the attribute matches a regular expression. This is also known as :format.
• :presence - Validates that the value is not nil and isn't empty (by checking for #empty?).

Adding a validator is simple:

module MyLibrary
  class MyValidator < Mixture::Validate::Base
    # This registers it with Mixture, so it can be used within a
    # `validate` call.
    register_as :my_validator

    def validate(record, attribute, value)
      # this sets instance variables mapping the above arguments.
      super
      my_super_awesome_validation
    end
  end
end

Adding a coercer is also simple:

module MyLibrary
  module Types
    class MyObject < Mixture::Types::Object
      options[:primitive] = nil
      constraint { |value| ... }
    end
  end
  module Coerce
    class MyObject < Mixture::Coerce::Base
      type MyLibrary::Types::MyObject

      coerce_to(Mixture::Types::Array) do |value|
        value.to_a
      end
    end
  end
end

Although the builtin coercers should do well.

A more complex example:

module MyLibrary
  class Something
    include Mixture::Model

    attribute :name, type: String
    attribute :files, type: Array[String]
    attribute :authors, type: Set[Author]
    attribute :dependencies, type: Set[Dependency]
  end
end

Bug reports and pull requests are welcome on GitHub at https://github.com/medcat/mixture. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.