Command Bus

Command Pattern - decoupling what is done from who does it.

Installation

Notice this gem is namespaced.

gem install arkency-command_bus

Usage

require'arkency/command_bus'command_bus=Arkency::CommandBus.newregister=command_bus.method(:register){FooCommand=>FooService.new(event_store: event_store).method(:foo),BarCommand=>BarService.new,}.map(&register)command_bus.(FooCommand.new)

New instance of a service for every command

If need a new instance of a service every time it is called with a command or you want to lazily load the responsible services, you can just use Proc during registration.

command_bus=Arkency::CommandBus.newcommand_bus.register(FooCommand,->(foo_cmd){FooService.new(event_store: event_store).foo(foo_cmd)})command_bus.register(BarCommand,->(bar_cmd){BarService.new.call(bar_cmd)})

Working with Rails development mode

In Rails development mode when you change a registered class, it is reloaded, and a new class with same name is constructed.

a=Usera.object_id# => 40737760 reload!# Reloading...b=Userb.object_id# => 48425300h={a=>1,b=>2}h[User]# => 2 a == b# => false 

so your Hash with mapping from command class to service may not find the new version of reloaded class.

To workaround this problem you can use to_prepare callback which is executed before every code reload in development, and once in production.

config.to_preparedoconfig.command_bus=Arkency::CommandBus.newregister=command_bus.method(:register){FooCommand=>FooService.new(event_store: event_store).method(:foo),BarCommand=>BarService.new,}.map(&register)end

and call it with

Rails.configuration.command_bus.call(FooCommand.new)

Convenience alias

require'arkency/command_bus/alias'

From now on you can use top-level CommandBus instead of Arkency::CommandBus.

About

Command Bus is funded and maintained by Arkency. Check out our other open-source projects.

You can also hire us or read our blog.