Class: RailsEventSourcing::BaseEvent

Inherits:
ActiveRecord::Base
  • Object
show all
Defined in:
lib/rails-event-sourcing/base_event.rb

Overview

This is the BaseEvent class that all Events inherit from. It takes care of serializing ‘data` and `metadata` via json It defines setters and accessors for the defined `data_attributes` After create, it calls `apply` to apply changes.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.aggregate_name ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 73

def aggregate_name
  inferred_aggregate = reflect_on_all_associations(:belongs_to).first
  raise "Events must belong to an aggregate" if inferred_aggregate.nil?

  inferred_aggregate.name
end

.data_attributes(*attrs) ⇒ Object

Define attributes to be serialize in the ‘data` column. It generates setters and getters for those.

Example:

class MyEvent < RailsEventSourcing::BaseEvent

data_attributes :title, :description, :drop_id

end



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# File 'lib/rails-event-sourcing/base_event.rb', line 88

def data_attributes(*attrs)
  @data_attributes ||= []

  attrs.map(&:to_s).each do |attr|
    @data_attributes << attr unless @data_attributes.include?(attr)

    define_method attr do
      self.data ||= {}
      self.data[attr]
    end

    define_method "#{attr}=" do |arg|
      self.data ||= {}
      self.data[attr] = arg
    end
  end

  @data_attributes
end

.event_name ⇒ Object

Underscored class name by default. ex: “post/updated” Used when sending events to the data pipeline



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# File 'lib/rails-event-sourcing/base_event.rb', line 110

def event_name
  name.underscore
end

.events_for(aggregate) ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 114

def events_for(aggregate)
  where(aggregate_name => aggregate)
end

.reserved_column_names ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 118

def reserved_column_names
  %w[id created_at updated_at]
end

Instance Method Details

#aggregate ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 25

def aggregate
  public_send aggregate_name
end

#aggregate=(model) ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 29

def aggregate=(model)
  public_send "#{aggregate_name}=", model
end

#aggregate_id ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 43

def aggregate_id
  public_send "#{aggregate_name}_id"
end

#aggregate_id=(id) ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 33

def aggregate_id=(id)
  public_send "#{aggregate_name}_id=", id
end

#apply(aggregate) ⇒ Object

Apply the event to the aggregate passed in. Must return the aggregate.

Raises:

  • (NotImplementedError) 


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# File 'lib/rails-event-sourcing/base_event.rb', line 39

def apply(aggregate)
  raise NotImplementedError
end

#build_aggregate ⇒ Object 



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# File 'lib/rails-event-sourcing/base_event.rb', line 47

def build_aggregate
  public_send "build_#{aggregate_name}"
end

#rollback! ⇒ Object

Rollback an aggregate entity to a specific version

Update the aggregate with the changes up to the current event and destroys the events after



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# File 'lib/rails-event-sourcing/base_event.rb', line 55

def rollback!
  base_class = self.class.superclass == RailsEventSourcing::BaseEvent ? self.class : self.class.superclass
  new_attributes = aggregate.class.new.attributes
  preserve_columns = new_attributes.keys - base_class.reserved_column_names
  new_attributes.slice!(*preserve_columns)
  aggregate.assign_attributes(new_attributes)
  aggregate.transaction do
    base_class.events_for(aggregate).where('id > ?', id).destroy_all
    base_class.events_for(aggregate).reorder('id ASC').each do |event|
      event.apply(aggregate)
    end
    aggregate.save!
  end
end