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Defining Output

Defining the output structure of a feature in Ductape specifies the expected result or data format produced by a feature's execution. The output is described using the output field of IProductFeature:

output: Record<string, string | Record<string, string | object>>

Outputs can dynamically reference values generated during the feature's event sequence, allowing you to map results from inputs, events, variables, and constants into a structured output object.

Output Mapping Syntax​

You can use special notations to reference values from different sources:

NotationDescription
$Input{field}Retrieves a value directly from the feature's input
$Sequence{sequence}{event}{key}Accesses a specific key from an event within a sequence
$Variable{app_tag}{key}References a variable associated with the app identified by app_tag
$Constant{app_tag}{key}Accesses a constant defined for the app identified by app_tag

Example: Output Definition​

{
  name: `$Input{name}`,   // Retrieves the "name" field from the initial input
  details:  {
    transaction_id: `$Sequence{process_payments}{debit_payment}{trx_id}`,
    timestamp: `$Sequence{process_payments}{settle_payment}{timestamp}`,
    user_role: `$Variable{user_service}{role}`,
    currency: `$Constant{payments}{currency_code}`
  }
}

In this example:

  • $Input{name}: References a value from the initial feature input (name field).
  • $Sequence{process_payments}{debit_payment}{trx_id}: Retrieves trx_id from a specific event within a sequence.
  • $Variable{user_service}{role}: Pulls the role value from a variable defined within the user_service app.
  • $Constant{payments}{currency_code}: Retrieves a constant value from the payments app.

Tip: You can nest objects in the output to create structured results, but the values should be mapped using the supported notations above.

Best Practices​

  • Use clear and descriptive output field names that match your API or business requirements.
  • Map only the necessary values to the output to keep responses concise.
  • Use the output mapping notations to dynamically reference data from inputs, events, variables, and constants.
  • Document the purpose of each output field for maintainability.

See Also​