Introduce typed event payload

[badenkov]

Hello!

I found interesting example in presentation of Nikita Shilnikov

module Events
  class PasswordChanged < Dry::Struct
    attribute :user_id, Types::UUID
    attribute :password, Types::String
  end

  class EmailChanged < Dry::Struct
    attribute :user_id, Types::UUID
    attribute :email, Types::String
  end

  Updated = PasswordChanged | EmailChanged
end

What do you think to use Dry::Struct for events?

IMHO it will make an application (where you will use events) more clear, we will see all possible events, and that events will have guaranteed shape.

[davydovanton]

Hello! Yep, I forgot to create issue for this but in future we want to use types for each event and use it like this:

events = Hanami::Events.initialize(:memory_sync)
events.subscribe('user.created') do |event_data|
 event_data # => object
end

Thanks for this issue! 👍

[badenkov]

It's a good news:)

Maybe would better:

module Events
  class UserCreated < Dry::Struct
    attribute :user_id, Types::UUID
    attribute :first_name, Types::String
   attribute :first_name, Types::String
  end
end

events.subscribe(Events::UserCreated) do |event_data|
 event_data # => object
end

What do you think?

[davydovanton]

so, I thought about something like this:

Event

class Users::Events::PasswordChanged < Hanami::Event::Type
  event_name 'user.password_changed'

  attribute :user_id, Types::UUID
  attribute :password, Types::String
end

Broadcaster

password_changed = Users::Events::PasswordChanged.new(payload)
events.broadcast(password_changed)

Subscriber

events.subscribe(Users::Events::PasswordChanged) do |object|
  object # => Users::Events::PasswordChanged
end

---

But it's just a idea now. Maybe we found better (from code and developer API) way how to build it ¯\_(ツ)_/¯

[badenkov]

That looks good. I liked it. Thanks for answers!

[smakagon]

@davydovanton @badenkov I like the idea of typed events. I've added PR with implementation. Let me know what you guys think about it.