Making Ruby || / && chaining for non nil/false values nicer

self_unless.rb

class Object
  # Usage:
  #   maybe_zero.self_unless(&:zero?) || zero_fallback
  #   # => either maybe_zero or zero_fallback (if maybe_zero was zero)
  def self_unless
    self unless yield(self)
  end
  
  # Usage:
  #   maybe_present.self_if(&:present?)
  #   # => maybe_present or false if maybe_present is not present (basically implementing http://apidock.com/rails/Object/presence)
  def self_if
    self if yield(self)
  end
end