class NilClass
  def blank?
    true
  end
end
 
class String
  def blank?
    self.strip.empty?
  end
end

这适用于nil.blank？和a_string.blank？你可以为真/假和一般对象扩展这个(就像rails一样)：

class FalseClass
  def blank?
    true
  end
end
 
class TrueClass
  def blank?
    false
  end
end
 
class Object
  def blank?
    respond_to?(:empty?) ? empty? : !self
  end
end

参考文献：

https://github.com/rails/rails/blob/2a371368c91789a4d689d6a84eb20b238c37678a/activesupport/lib/active_support/core_ext/object/blank.rb#L57
https://github.com/rails/rails/blob/2a371368c91789a4d689d6a84eb20b238c37678a/activesupport/lib/active_support/core_ext/object/blank.rb#L67
https://github.com/rails/rails/blob/2a371368c91789a4d689d6a84eb20b238c37678a/activesupport/lib/active_support/core_ext/object/blank.rb#L14
https://github.com/rails/rails/blob/2a371368c91789a4d689d6a84eb20b238c37678a/activesupport/lib/active_support/core_ext/object/blank.rb#L47

这是String.blank？实施应该比前一个更有效：

https://github.com/rails/rails/blob/2a371368c91789a4d689d6a84eb20b238c37678a/activesupport/lib/active_support/core_ext/object/blank.rb#L101