Class: FourthDimensional::CommandHandler

Inherits:
Object
  • Object
show all
Includes:
Eventable
Defined in:
lib/fourth_dimensional/command_handler.rb

Overview

FourthDimensional::CommandHandler

Command handlers have bindings that wrap a Command to load an aggregate and apply events.

class PostCommandHandler < FourthDimensional::CommandHandler
  on AddPost do |command|
    with_aggregate(PostAggregate, command) do |post|
      post.add(title: command.title, body: command.body)
    end
  end

  # manually load and save aggregate
  on UpdateTitle do |command|
    post = repository.load_aggregate(PostAggregate, command.aggregate_id)
    post.update_title(title: command.title)
    save(command, post)
  end

  on PublishPost do |command|
    with_aggregate(PostAggregate, command) do |post|
      post.publish
    end
  end
end

Defined Under Namespace

Classes: CommandAndEvents

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Eventable

included

Constructor Details

#initialize(repository:) ⇒ CommandHandler

Returns a new instance of CommandHandler.



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# File 'lib/fourth_dimensional/command_handler.rb', line 45

def initialize(repository:)
  @repository = repository
end

Instance Attribute Details

#repository ⇒ Object (readonly)

Returns the value of attribute repository.



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# File 'lib/fourth_dimensional/command_handler.rb', line 30

def repository
  @repository
end

Instance Method Details

#call(command) ⇒ Object

Invokes a callback for an command.



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# File 'lib/fourth_dimensional/command_handler.rb', line 50

def call(command)
  callback = self.class.event_bindings[command.class]
  return if callback.nil?
  instance_exec(command, &callback)
end

#save(command, aggregate) ⇒ Object

Saves the command and aggregate’s applied events

class PostCommandHandler < FourthDimensional::CommandHandler
  on AddPost do |command|
    post = repository.load_aggregate(PostAggregate, command.aggregate_id)
    post.add(title: command.title)
    save(command, post)
  end
end



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# File 'lib/fourth_dimensional/command_handler.rb', line 72

def save(command, aggregate)
  repository.save_command_and_events(CommandAndEvents.new(
    command: command,
    events: aggregate.applied_events
  ))
end

#with_aggregate(aggregate_class, command) {|aggregate| ... } ⇒ Object

Yields the aggregate and saves the applied events

Yields:

  • (aggregate) 


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# File 'lib/fourth_dimensional/command_handler.rb', line 57

def with_aggregate(aggregate_class, command, &block)
  aggregate = repository.load_aggregate(aggregate_class, command.aggregate_id)
  yield aggregate
  save(command, aggregate)
end