EventSourcery::Rails

Short description and motivation.

Usage

Commands

EventSourcery::Rails adds an optional base class for commands to enforce instantiating commands with an aggregate_id and required parameters as keyword arguments. Defined attributes are available with an attr_reader.

Includes ActiveModel::Validations for validating attributes.

```ruby class AddUser < EventSourcery::Rails::Command attributes :name, :email validates_presence_of :name, :email end

AddUser.new # => raises ArgumentError.new(“missing keywords: aggregate_id, name, email”)

command = AddUser.new(aggregate_id: ‘aggregate-id’, name: ‘name’, email: ‘email’) command.aggregate_id # => “aggregate-id” command.name # => “name” command.email # => “email”

command.valid? # => true ```

Command Handlers

You can also optionally include EventSourcery::Rails::CommandHandler to use use a callback DSL for binding commands. This DSL allows your application code to use all command handlers with #call.

Todo

• [ ] Consider switching to a base class with common initializer and with_aggregate
• [ ] Introduce API for invoking all known command handlers with an array of commands.

```ruby class UserCommandHandler include EventSourcery::Rails::CommandHandler

attr_reader :repository

def initialize(repository: EventSourceryRails.repository) @repository = repository end

on AddUser do |command| aggregate = repository.load(UserAggregate, aggregate_id) aggregate.add(name: command.name, email: command.email) repository.save(aggregate) end

on UpdateUserEmail do |command| aggregate = repository.load(UserAggregate, aggregate_id) aggregate.update_email(email: command.email) repository.save(aggregate) end end ```

Installation

Add the following line to your Gemfile.

ruby gem 'event_sourcery' gem 'event_sourcery-postgres' gem 'event_sourcery-rails'

Then run bundle install

Next, your need to run the generator:

bash $ rails generate event_sourcery_rails:install

At this point you will have an initializer to configure EventSourcery and the following Rake tasks.

bash $ rails event_sourcery:db:migrate # create the event sourcery schema $ rails event_sourcery:processors:setup # create projector schemas $ rails event_sourcery:processors:reset # drop and recreate projector schemas and data $ rails event_sourcery:processors:run # start event stream processors

Typically you’ll have the following in your Procfile.

yaml web: rails server processors: rails event_sourcery:processors:run

Contributing

Please submit issues and pull requests for bugs, features or ideas.

License

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