How to pass a value to step from class/instance scope?

Let's consider the following service:

class Service
  # ...

  step EscapeRegexp, \
    in: {pattern: ???}, # `???` is just a placeholder here, it is not a valid Ruby syntax.
    out: :escaped

  # ...
end

We need to pass ENV["PATH_PATTERN"] to the EscapeRegexp step as the pattern param.

How that can be achievable?

There are multiple ways:

• Using raw.

  step EscapeRegexp, \
    in: {pattern: raw(ENV["PATH_PATTERN"])},
    out: :escaped

  This is how step call is "translated" to regular service invocation under the hood:

  def step_result
    @step_result ||= EscapeRegexp.result(pattern: ENV["PATH_PATTERN"])
  end

  Since raw is a class method you can pass it anything from the enclosing class scope.

  The value is forwarded without any intermediate processing.

  step EscapeRegexp, \
    in: {pattern: raw(any_class_method)},
    out: :escaped

• Using proc form.

  step EscapeRegexp, \
    in: {pattern: -> { ENV["PATH_PATTERN"] }},
    out: :escaped

  The proc form does not additionally process the passed value as well, but it is evaluated in the instance scope.

  So you can access any service instance methods in it.

  step EscapeRegexp, \
    in: {pattern: -> { any_instance_method }},
    out: :escaped

info

Check the Step to Result Translation table for more detailed reference.