https://github.com/baylorrae/event_sourcery-rails
Combining two great powers for data and web.
https://github.com/baylorrae/event_sourcery-rails
Last synced: 2 months ago
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Combining two great powers for data and web.
- Host: GitHub
- URL: https://github.com/baylorrae/event_sourcery-rails
- Owner: BaylorRae
- License: mit
- Created: 2019-02-09T19:02:40.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2019-02-10T18:18:00.000Z (over 7 years ago)
- Last Synced: 2025-02-28T11:39:49.161Z (over 1 year ago)
- Language: Ruby
- Size: 46.9 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: MIT-LICENSE
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README
# EventSourcery::Rails
[](https://travis-ci.org/BaylorRae/event_sourcery-rails)
I wanted to add [Event Sourcing][event_sourcing_fowler] to my Rails application
and after using several libraries/framework settled on EventSourcery from
Envato. After creating a demo application based on their todo example with Rails
I realized the installation steps are pretty simple. With this gem it can be
installed and configured with a single rake task!
In addition to automating the install, I also wanted to incorporate the DSL from
Sequent and RailsEventStore for commands and command handlers. I like the
command handler itself wrapping single responsibility around an aggregate with
the `on` command binding. I also wanted to remove the boilerplate for
instantiating and validating commands since we can load
`ActiveModel::Validations` for free.
- [Installation](#installation)
- [Usage](#usage)
- [Commands](#commands)
- [Command Handlers](#command-handlers)
- [Contributing](#contributing)
- [License](#license)
## 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
```
## 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`][active_model_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
```
## 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](https://opensource.org/licenses/MIT).
[event_sourcing_fowler]: https://martinfowler.com/eaaDev/EventSourcing.html
[active_model_validations]: https://api.rubyonrails.org/classes/ActiveModel/Validations.html#module-ActiveModel::Validations-label-Active+Model+Validations