outputs.md

Outputs

Outputs are the results of a service.

TL;DR

• Define outputs using the output keyword in the service class
• Outputs can have default values
• Outputs can be validated by type [In Development]

Define Outputs

You define outputs using the output keyword in the service class.

class AI::Chat < ApplicationService
  output :messages
  output :cost
end

Write Outputs

Outputs function similarly to instance variables created with attr_accessor.

class AI::Chat < ApplicationService
  # Steps
  step :chat

  # Outputs
  output :messages
  output :cost

  private

  def chat
    self.messages = ["Hello!", "Hi, how are you?"]
    self.cost = 0.0013
  end
end

To set outputs programmatically, use the outputs.set method or hash syntax.

class AI::Chat < ApplicationService
  # ...

  def chat
    outputs.set(:messages, ["Hello!", "Hi, how are you?"])
    outputs.set(:cost, 0.0013)

    # Or use hash syntax

    outputs[:messages] = ["Hello!", "Hi, how are you?"]
    outputs[:cost] = 0.0013
  end
end

Type Validation

You can specify the type of output using the type option. The output type will be validated when the service successfully completes.

class AI::Chat < ApplicationService
  output :messages, type: Array
  output :cost, type: :float
end

You can specify multiple allowed types using an array.

class AI::Chat < ApplicationService
  output :result, type: [String, Hash]
end

Default Values

Set default values for outputs using the default option. The default value will be automatically set before the execution of steps.

class AI::Chat < ApplicationService
  output :cost, default: 0.0
end

Removing Inherited Outputs

When inheriting from a parent service, you can remove outputs using remove_output:

class BaseReportService < ApplicationService
  output :report
  output :debug_info
end

class ProductionReportService < BaseReportService
  # Don't expose debug info in production
  remove_output :debug_info
end

What's Next?

Next, learn about context.

Next: Context