ucasy

Ucasy

Description soon!

Installation

Add this line to your application's Gemfile:

gem "ucasy", "~> 0.2.0"

And then execute:

bundle install

Or install it yourself as:

bundle add ucasy

Create base file

You can use a Rails generator to create setup UseCaseBase file:

rails g ucasy:install

This will create app/use_cases/use_case_base.rb

class UseCaseBase < Ucasy::Base
  class Flow < Ucasy::Flow
  end
end

Basic usage

You can create a simple use case to app/use_cases/authenticate_user.rb:

class AuthenticateUser < UseCaseBase
  def before
    context.user = User.find_by(login: context.login)
  end

  def call
    return if context.user.valid_password?(context.password)

    context.fail!(
      status: :unprocessable_entity,
      message: "User not found",
      errors: context.user.errors
    )
  end

  def after
    UserMailer.with(user: context.user).login_warning.perform_later
  end
end

Using methods

There is some methods to ensure arguments for each use case:

required_attributes

class AuthenticateUser < UseCaseBase
  required_attributes(:login, :password)

  def call
    context.login
    context.password
  end
end

The method required_attributes raises an error if login or password is blank

validate

You can use ActiveModel or any class that respond to valid?, errors, present? and accepts a hash as arguments to validate you payload.

Create a class

class AuthenticateUser < UseCaseBase
  validate(AuthenticateUserValidation)

  def call
    context.login
    context.password
  end
end

You can filter attributes. Only context.login and context.password will be validated in example below:

class AuthenticateUser < UseCaseBase
  validate(AuthenticateUserValidation, :login, :password)
  ...
end

Adds a validation

class AuthenticateUserValidation
  include ActiveModel::Model

  attr_accessor :login, :password

  validates :login, presence: true
  validates :password, presence: true

  def to_context
    {login:, :password} # this hash will be injected in use cases context
  end
end

Using Flow

You can also create a flow to organize your use cases:

class PlaceOrder < UseCaseBase::Flow
  transactional # if any use case fails ActiveRecord will rollback transaction

  validate(PlaceOrderValidation)

  flow(ChargeCard, SendThankYou, FulfillOrder)
end

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/ucasy.

License

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