Avoiding a lot of ifs in Ruby

Question

I have a serious nesting of ifs in a helper code and I would like to making cleaner. I would like to avoid case if possible as well.

I know there is probably a more Object-Oriented approach to this but I can't seem to know how.

I'm flooded with stuff like this:

  def print_flight_options_status(invitation)
    if invitation.group.travel_class == 'none'
      not_allowed
    elsif invitation.refused_flight_options?
      not_needed
    elsif invitation.selected_flights?
      waiting_reservation
    elsif invitation.flight_options.empty?
      not_sent_yet
    elsif invitation.requested_more_flight_options?
      rejected
    else
      waiting_guest_input
    end
  end

  def print_event_terms_status(invitation)
    if invitation.event_terms_status.nil?
      "<span class='grey_highlight pj_cat'>Aguardando</span>"
    elsif invitation.accepted_event_terms?
      "<span class='green_highlight pj_cat'>Aceito</span>"
    elsif invitation.rejected_event_terms?
      "<span class='red_highlight pj_cat'>Declinado</span>"
    elsif invitation.cancelled_event_terms?
      "<span class='yellow_highlight pj_cat'>Cancelado</span>"
    end.html_safe
  end

Is there a better/simpler way?

Thank you!

Answer 1

I prefer this style:

  def print_flight_options_status(invitation)
    return not_allowed         if invitation.group.travel_class == 'none'
    return not_needed          if invitation.refused_flight_options?
    return waiting_reservation if invitation.selected_flights?
    return not_sent_yet        if invitation.flight_options.empty?
    return rejected            if invitation.requested_more_flight_options?

    waiting_guest_input
  end

UPD

About second code-snippet. I think in this case you can use decorators (for example draper) for invitations, so:

def print_event_terms_status(invitation)
  InvitationDecorator.decorate(invitation).status_in_html
end

Where InvitationDecorator:

class InvitationDecorator < Draper::Base
  def status_in_html
    if invitation.event_terms_status.nil?
      "<span class='grey_highlight pj_cat'>Aguardando</span>"
    ...
  end
end

Answer 2

There is a case-variant which may be a bit better:

x = ''
case 
  when x == 'xxy'
    puts '=xxy'
  when x.empty?
    puts 'is empty'
  else
    puts "well, I don't know, what it is"
  end

In your case, you could use:

def print_flight_options_status(invitation)
  case
    when invitation.group.travel_class == 'none'
      not_allowed
    when invitation.refused_flight_options?
      not_needed
    when invitation.selected_flights?
      waiting_reservation
    when invitation.flight_options.empty?
      not_sent_yet
    when invitation.requested_more_flight_options?
      rejected
    else
      waiting_guest_input
    end
  end  

---

You may also define a kind of with-statement:

module With
  def with(&block)
    self.instance_eval &block
  end
end

['a', ''].each{|test|
  test.extend(With)
  p test.with{
    if empty? 
      :empty
    elsif self == 'a'
      :a
    else
      :else
    end
  }  
}

In your case:

def print_flight_options_status(invitation)
  invitation.extend(With)
  invitation.with{
    if group.travel_class == 'none'
        not_allowed
      elsif refused_flight_options?
        not_needed
      elsif selected_flights?
        waiting_reservation
      elsif flight_options.empty?
        not_sent_yet
      elsif requested_more_flight_options?
        rejected
      else
        waiting_guest_input
      end
    }
  end  

Advantage: You don't need to repeat invitation..

Answer 3

IMHO both variants look ok regarding ifs. They clearly express business logic and well formatted. Maybe I'd separate a bit markup from UI Logic:

def print_event_terms_status(invitation)
  span = 
    ->(cls, text) { "<span class='#{class} pj_cat'>#{text}</span>".html_safe }
  if invitation.event_terms_status.nil?
    span['grey_highlight', 'Aguardando']
  elsif invitation.accepted_event_terms?
    span['green_highlight', 'Aceito']
  elsif invitation.rejected_event_terms?
    span['red_highlight', 'Declinado']
  elsif invitation.cancelled_event_terms?
    span['yellow_highlight', 'Cancelado']
  end
end