How to understand nil vs. empty vs. blank in Ruby

Question

I find myself repeatedly looking for a clear definition of the differences of nil?, blank?, and empty? in Ruby on Rails. Here\'s the

Answer 1

Rails 4

an alternative to @corban-brook 's 'Array gotcha: blank?' for checking if an arrays only holds empty values and can be regarded as blank? true:

[ nil, '' ].all? &:blank? == true

one could also do:

[nil, '', "", " ",' '].reject(&:blank?).blank? == true