AshCommanded DSL Cheatsheet

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Resource Configuration 

defmodule MyApp.User do
  use Ash.Resource,
    extensions: [AshCommanded.Commanded.Dsl]
    
  # Resource configuration...
    
  commanded do
    # Commanded DSL configuration...
  end
end

Command Definition 

commanded do
  commands do
    command :register_user do
      fields [:id, :name, :email]
      identity_field :id
      action :register
      
      # Optional settings
      command_name :RegisterUser
      autogenerate_handler? true
      handler_name :handle_register
      in_transaction? true
      repo MyApp.Repo
      
      # Advanced options
      middleware [MyApp.LoggingMiddleware]
      
      # Parameter transformations
      transform_params do
        map email: :normalized_email
        compute :timestamp, &DateTime.utc_now/0
      end
      
      # Parameter validations
      validate_params do
        validate :email, format: ~r/@/
        validate :name, present: true
      end
      
      # Alternative transaction syntax
      transaction do
        enabled? true
        repo MyApp.Repo
        timeout 5000
        isolation_level :read_committed
      end
      
      # Context options
      include_aggregate? true
      include_command? true
      include_metadata? true
      context_prefix :cmd
    end
  end
end

Event Definition 

commanded do
  events do
    event :user_registered do
      fields [:id, :name, :email]
      
      # Optional settings
      event_name :UserRegistered
    end
  end
end

Projection Definition 

commanded do
  projections do
    projection :user_registered do
      # Define the Ash action to invoke
      action :create
      
      # Static changes
      changes(%{
        status: "active"
      })
      
      # Or dynamic changes via function
      changes(fn event ->
        %{
          id: event.id,
          name: event.name,
          email: event.email,
          registered_at: DateTime.utc_now()
        }
      end)
      
      # Optional settings
      autogenerate? true
      projector_name :CustomUserProjector
    end
  end
end

Event Handler Definition 

commanded do
  event_handlers do
    # Function-based handler
    handler :notification_handler do
      events [:user_registered]
      action fn event, _metadata ->
        MyApp.Notifications.send_welcome_email(event.email)
        :ok
      end
    end
    
    # Ash action handler
    handler :external_sync do
      events [:user_registered]
      action :sync_to_crm
      idempotent true
    end
    
    # PubSub publishing handler
    handler :event_broadcaster do
      events [:user_registered, :email_changed]
      publish_to "user_events"
    end
    
    # Optional settings
    handler :custom_name_handler do
      events [:user_registered]
      action fn _, _ -> :ok end
      handler_name :CustomHandler
      autogenerate? true
    end
  end
end

Application Configuration 

defmodule MyApp.Domain do
  use Ash.Domain, extensions: [AshCommanded.Commanded.Dsl]
  
  resources do
    resource MyApp.User
  end
  
  commanded do
    application do
      otp_app :my_app
      event_store Commanded.EventStore.Adapters.EventStore
      
      # Optional settings
      pubsub :local
      registry :local
      include_supervisor? true
      
      # Snapshotting
      snapshotting true
      snapshot_threshold 100
      snapshot_version 1
      snapshot_store MyApp.CustomSnapshotStore
    end
  end
end