Exemplo de rake task com Functional Objects (Rubyconf Brasil 2018)

Rakefile

class TaskArgumentsCalculator
  def initialize(operator)
    @operator = operator
  end

  def call(_task, args)
    puts map_numbers(args).reduce(&@operator)
  end

  def to_proc
    -> (*args) { call(*args) }
  end

  private

  def map_numbers(args)
    [:a, :b].map { |key| args[key].to_f }
  end
end

SumTaskArgs = TaskArgumentsCalculator.new(:+)
SubtractTaskArgs = TaskArgumentsCalculator.new(:-)

desc 'adds two numbers'
task :sum, [:a, :b], &SumTaskArgs

desc 'subtract two numbers.'
task :sub, [:a, :b], &SubtractTaskArgs