[RUBY] [Rails] Check the contents of the object

What is an object? Objects are like "boxes". Therefore, when checking for existence,

Let's look at it from the perspective of.

Does the box itself not exist? Nil?



Is the box empty? Empty?



Does the box itself not exist? Is the content empty even if it is done? Blank?

"The box does not exist or the contents do not exist" By the way, ** Rails-only method **



obj.nil? || obj.empty?

Isn't the box itself existing and empty? Present?

"There is a box and there are contents" By the way, ** Rails-only method **



!obj.nil? && !obj.empty?

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