What is a step proc input?

  • A step proc input, also called an inline step input, evaluates a Proc in the organizer's instance scope at run time and passes the returned value to the step. It is written as {step_parameter_name: -> { ... }} in in:.

    class CalculateDoubled
  include ConvenientService::Standard::Config

  attr_reader :number

  def initialize(number:)
    @number = number
  end

  def result
    success(doubled: number * 2)
  end
end

class AwardLoyaltyPoints
  include ConvenientService::Standard::Config

  step CalculateDoubled,
    in: {number: -> { base_points * multiplier }},
    out: {doubled: :points}

  private

  def base_points
    7
  end

  def multiplier
    3
  end
end

result = AwardLoyaltyPoints.result

result.success?
# => true

result.data[:points]
# => 42

  • The proc is evaluated via instance_exec on the organizer, so it has access to the organizer's instance methods and state - here, base_points and multiplier inside the lambda refer to AwardLoyaltyPoints's own private methods.

  • Both -> { ... } and proc { ... } work - any Proc is accepted.

  • Like a step raw input, a step proc input does not go through any additional processing - the only difference is the scope it is evaluated in: instance scope for a proc input, class scope for a raw input.

  • Use a step proc input when a step needs a value computed at run time from the organizer's own methods, constants, or state, without extracting that computation into its own organizer method first - here, base_points * multiplier is written inline at the step declaration instead of behind a dedicated method that a usual step input or a step alias input would have to reference.

See also

Sources