wdl.rb

class Workflow
  attr_accessor :name, :inputs

  def to_s
    "workflow #{name} {\n".tap do |result|
      inputs.each do |input|
        result << "#{input.to_s}\n"
      end
      result << "}"
    end
  end
end

class FileInput
  attr_accessor :name

  def to_s
    "File #{name}"
  end
end

wdl = Workflow.new

wdl.name = 'hello'

file = FileInput.new
file.name = 'myfile'

wdl.inputs = [file]

wdl.to_s